Table of Contents
What is peak detector
A peak detector is an electronic circuit that is used to detect the peak value of an input signal. It is commonly used in applications where it is necessary to determine the maximum value of a waveform over a certain period of time, such as in audio processing or radio communication systems. The peak detector works by comparing the input signal to a reference voltage, and whenever the input signal exceeds the reference voltage, the peak detector stores the value as the peak. The peak detector then holds this value until the input signal drops below the reference voltage, at which point it resets and begins tracking the next peak value. The output of a peak detector is therefore a voltage that represents the peak value of the input signal. The design of a peak detector can vary, but it typically consists of a comparator, a diode, and a storage capacitor. The choice of components and the configuration of the circuit will determine the performance of the peak detector, including its accuracy, speed, and response time.
How peak detector works
A peak detector works by continuously monitoring an input signal and storing its maximum value, or peak. The circuit typically consists of a comparator, a diode, and a storage capacitor. The comparator compares the input signal to a reference voltage, and whenever the input signal exceeds the reference voltage, the comparator outputs a high voltage to the diode. The diode allows the high voltage to pass through to the storage capacitor, which charges to the peak value of the input signal. The storage capacitor holds this value until the input signal drops below the reference voltage, at which point the comparator outputs a low voltage and the diode blocks any further charging of the storage capacitor. The output of the peak detector is therefore a voltage that represents the peak value of the input signal. The response time, accuracy, and stability of the peak detector depend on the design of the circuit and the choice of components.
The output voltage of a peak detector can be described mathematically as follows:
V_out = V_peak(t) * e^(-t/τ)
where:
V_out = output voltage of the peak detector
V_peak(t) = peak value of the input signal at time t
τ = time constant of the peak detector, which is determined by the values of the storage capacitor and the load resistor
t = time elapsed since the peak was detected
The time constant τ can be calculated as follows:
τ = RC
where:
R = load resistor C = storage capacitor
The time constant determines the speed at which the output voltage decays after the peak has been detected. A smaller time constant means that the output voltage decays more quickly, while a larger time constant means that the output voltage decays more slowly. The choice of time constant will depend on the specific requirements of the application and the desired performance of the peak detector.
Peak detector circuit
Peak detector circuit is an electronic circuit that is used to detect the peak value of an input signal. It is typically composed of three main components: a comparator, a diode, and a storage capacitor. The comparator compares the input signal to a reference voltage, and whenever the input signal exceeds the reference voltage, the comparator outputs a high voltage to the diode. The diode allows the high voltage to pass through to the storage capacitor, which charges to the peak value of the input signal. The storage capacitor holds this value until the input signal drops below the reference voltage, at which point the comparator outputs a low voltage and the diode blocks any further charging of the storage capacitor. The output of the peak detector is therefore a voltage that represents the peak value of the input signal. The performance of the peak detector, such as its accuracy, speed, and response time, can be adjusted by selecting the appropriate values for the reference voltage, the load resistor, and the storage capacitor. A peak detector circuit can be useful in a wide range of applications, such as audio processing, radio communication systems, and power supply monitoring.
Diode detector
Diode detectors are the most simple, yet extremely efficient kind of detector. Every crystal radio utilizes this kind of detector and the crystal that is used is simply a diode as well as an electronic diode. Because these kinds of receivers typically had just the detector, with no additional circuitry , they were usually known as “Detectors” (not Detephones, which was the name used to describe the type of receiver produced from PZT). Although it had its advantages for the first ten years or so of tube receivers, this kind of detection was rarely utilized. What was the reason? It’s because of economics. The diode detector didn’t offer any amplifying capabilities in the first place, and at a time where each tube was an expensive accessory to the receiver, such an expensive devices like a low-sensitivity detector was not feasible to afford.
Whatever how complex the device (number of circuits, tubes and so on. ) The diode detector is able to be integrated into the circuit exactly the same way and in reality, based on the place where the diode will be connected, it can be done in two ways. Based on the way in which the diode detector is employed it is referred to as an analog or a series detector. As you can see in the diagrams that are later posted in the text the name of the detector is derived from the manner in which the detector is connected with the circuit. If it’s connected in parallel to the output and input of the detector, then we speak of a serial detector. However, when it is connected in parallel, we are talking about an asynchronous detector. A series detector could be discovered mostly in crystal receivers in which it was the basis for nearly 100 percent of all designs. It is also present in modern circuits made with semiconductor diodes. In tube receivers employing vacuum diodes for detection the majority of parallel circuits were employed. The choice of circuits was influenced by the design specifications, and for a parallel detector, it was simple to get an ARW voltage. In addition this detector permitted the cathode for the diode to be linked to the lamp to the cathodes of other systems within the same lamp as for the ABC1 lamp. This significantly streamlined the process of the production of lamps.
Series detector
It is well-known that any diode regardless of the kind (tube or silicon crystal) can only pass current one way. In a circuit for detecting series as the circuit’s schematic is illustrated in the opposite figure that, the diode D will only pass positive half that of the present. The current passes via into the receiver (indicated by the symbol of the resistor) R1. It’s still very high-frequency, but because of the truncation in its negative component this current has a non-zero average value. The value of the average will be proportional to width of the positive and negative halves of input signals. It corresponds to the low frequency signal that is modulating the radio signal. When the receiver is an earphone even though a high-frequency signal is also flowing across it, it is feasible to listen for the broadcast within it because an average of current will be similar to the modulating acoustic sound.
Blue color – current of input with high frequencies.
The color purple is a result of output voltage is too low a time steady
Color red – voltage output the too high rate of time continuous
The black color is output at the voltage at the optimal time at a constant rate
Green color is the mean value of the voltage output
The voltage and current waves of the diode detector are illustrated in the opposite figure. The blue line represents that the input frequency is high. The diode, as per its principle of operation, carries the current in one direction. When it is being turned on, as shown in the diagram above the upper or positive half of the output signal. Because the signal generated by the diode at the resistor R1 cannot be symmetrical regard towards zero (it will always be positive, or at least the same as zero) it is an un-zero average. As you can see from the image that the magnitude of this typical number (green lines in the image) is not significant in comparison to input signals that is one of the weaknesses of this detector that is the most simplified and the other is there is a huge high-frequency component that is at the output. However, despite its shortcomings due to its utmost efficiency, this circuit was widely used in the early days of radio technology as crystal detectors due to its other advantages . The detector’s crystal is extremely cheap and the circuit doesn’t require any additional power source to operate thus its operation will not incur any additional expenses.
As we have mentioned the diode operates solely in one direction, and it is produced by a voltage that’s always positive. That means that at the output there is, in addition to that alternating frequency, there’s an DC voltage, which is higher than the signal is present at the detector’s input. The voltage isn’t very useful as the sound wave is an alternating electric current, however, it does have one primary application in radios – ARW, also known as Automatic Gain Control. If the signal is high (e.g. when we’re receiving a powerful station) it may cause excessive power to the receiver, which can result in an unpleasant sound. In the event that the increase is minimal enough to ensure that the receiver will not be impacted by the overdrive which means that, when it is the reception of weak stations cannot be achieved – the receiver will suffer from a deficiency of gain. In addition to these extreme situations, ARW causes different stations with differing levels of receive HF signals and play at the same volume. Moreover, when the level of HF signal fluctuates (which is quite common, particularly for medium and short-waves) it will maintain a constant broadcast volume irrespective of variations. This is why the constant signal with an intensity proportional to strength of the signal is extremely useful because it will instantly alter the gain of the receiver to correspond to the intensity of the signal.
A minor change can allow you to improve slightly the characteristics that the device. It involves including to the circuit an capacitor with adequate capacity. The diode current, in turn, positively charge the capacitor C2 with a voltage equivalent to the maximum volume of input signals. If there was no load R1 within this circuit (or the resistance of the load would be quite high) and the capacitor will be charged to the voltage at which it is and remain at this level for a long time, and at output, we’d see DC voltages equivalent to the input voltage at its maximum which is appropriate for an ARW detector however, not for a detector of audio signals. This is why the resistor R1 adds to the circuit to ensure that because it is the only way C2 the capacitor can discharge. The waveforms of the circuit that have capacitor C2 are represented by red, black as well as purple lines.
The amount of resistance in this resistor or, more specifically the sum of the capacitance of the capacitor as well as that of its resistor, is vital – it can’t be too big or small as the capacitor will discharge quicklyor discharge in a slow manner. The RC circuit is a type of low-pass filter that must block the high-frequency resonance, but let the low-frequency waveform go. This is further complicated due to the fact that it’s a nonlinear circuit where there is a different current used for charging the capacitor, and another one is used that is used to drain it. The waveform that appears for various time constants in the R1C2 circuit can be seen in the image opposite. It is evident that if the time constant is too small, it’s signal (marked in the red line) disappears too quickly, and the waveform at output, rather than being an attractive and smooth low-frequency sine wave, is exactly as the circuit with no capacitor that is high-frequency single pulses, but slightly larger. When the frequency is too constant the voltage drop will be extremely small. If the next highest frequency of the input waveform is not high enough, it won’t be visible – the output waveform will be blurred – this is evident in the red lines.
The ideal waveform is represented through the line of black. When you first look at the graph, it doesn’t look great as it is evident that the ripples in the higher-frequency signal remain extremely large, but it’s still far superior to that blue-colored signal. However, in reality the frequency difference of the smaller (modulating audio signals) and the large (modulating transport signal) is significantly greater (it is reduced in the graph in order to make it more legible) and can range anywhere from a dozen to thousands of times, or on average, about 100 it is quite easy to satisfy this requirement in real life. The typical time-invariant is around 100ms. Also, the differences in the frequency of successive added portions of the waveform of the HF. (blue figure) image) is so small it is that “jaggedness” of the output waveform is virtually undetectable and can be easily removed by our ears and the other receiver stages. As you can see, the magnitude in the m.cz. signals (black stripe) in the circuit that has capacitors is higher than the value for the diode on its own which is why we saw an additional increase in sensitivities to the detection.
In the circuit the diode’s direction is able to be reversed. In this case, the circuit will operate the same with the only difference being that it is that the negative half of the high frequency current pass while the positive half are blocked. All of the characteristics in charging capacitors and charging capacitors, with time constants are exactly the same. The only difference is the changing of the polarity the voltages generated at the output changing from negative to positive and the drawing of the waves is identical but it will be drawn under the X-axis and not over it, as illustrated in the image opposite. In the explanation the scenario of passing the positive and negative halves the signal was discussed because that is the way serial detectors are typically constructed in real life.
Active peak detector
An active peak detector is a type of peak detector circuit that uses an active component, such as an operational amplifier (op-amp), to achieve its function. Unlike passive peak detectors, which rely on passive components such as resistors and capacitors to store and discharge energy, active peak detectors use the amplification capability of an op-amp to detect and hold the peak value of a signal. The active peak detector operates by continuously comparing the input signal to a reference voltage and storing the maximum value of the signal.
Active peak detectors have several advantages over passive peak detectors, including increased accuracy, faster response time, and better signal-to-noise ratio. They can be used in a wide range of applications, such as audio processing, power supply control, and instrumentation, to detect the peak value of a signal and hold it for a specified time period.
The design of an active peak detector circuit typically involves an op-amp configured in a comparator or a peak detector configuration, a diode to rectify the input signal, and a storage capacitor to hold the peak voltage. The output of the op-amp is connected to the storage capacitor through the diode, allowing the capacitor to charge to the peak voltage when the input signal is greater than the reference voltage. When the input signal drops below the reference voltage, the capacitor discharges through a discharge resistor, maintaining the peak voltage until the next peak is detected.
Op amp peak detector
An operational amplifier (op amp) peak detector is a type of peak detector circuit that uses an operational amplifier as the comparator. An operational amplifier is an integrated circuit that is designed to perform mathematical operations, such as amplification and comparison, on input signals. In a peak detector circuit, the operational amplifier is used to compare the input signal to a reference voltage and determine whether the input signal has exceeded the reference voltage.
When the input signal exceeds the reference voltage, the operational amplifier outputs a high voltage, which is then passed through a diode to a storage capacitor. The storage capacitor charges to the peak value of the input signal, and the voltage across the storage capacitor represents the peak value. The storage capacitor is typically connected to a load resistor, which is used to discharge the storage capacitor when the input signal drops below the reference voltage.
The performance of an op amp peak detector can be optimized by selecting the appropriate values for the reference voltage, the load resistor, and the storage capacitor. The reference voltage determines the threshold at which the peak detector starts to detect the peak value, while the load resistor and the storage capacitor determine the speed and stability of the peak detector. A smaller load resistor and a larger storage capacitor will result in a slower, more stable peak detector, while a larger load resistor and a smaller storage capacitor will result in a faster, less stable peak detector.
Op amp peak detectors are widely used in a variety of applications, including audio processing, power supply monitoring, and radio communication systems. They are especially useful in applications where a fast and accurate measurement of the peak value of an input signal is required.
In conclusion, an op amp peak detector is a useful and versatile type of peak detector circuit that can be optimized for different applications by selecting the appropriate values for the reference voltage, the load resistor, and the storage capacitor. It is an essential component in many electronic systems, and its popularity is due to its accuracy, speed, and ease of use.
Digital peak detector
A digital peak detector is a type of peak detector circuit that uses digital signals and digital processing elements, such as microcontrollers or field-programmable gate arrays (FPGAs), to detect the peak value of an input signal. Unlike analog peak detectors, which use analog components such as operational amplifiers and capacitors to detect the peak value, digital peak detectors use digital signals and digital processing to perform the same function.
In a digital peak detector, the input signal is typically converted from an analog signal to a digital signal using an analog-to-digital converter (ADC). The digital signal is then processed by a microcontroller or FPGA to determine the peak value. The peak value is stored in a digital memory, such as a register or a memory array, and can be retrieved and processed as needed.
Digital peak detectors offer several advantages over analog peak detectors, including improved accuracy and greater flexibility. For example, digital peak detectors can be easily programmed and reconfigured to suit different applications and to perform different functions. They can also be used in conjunction with other digital processing elements, such as digital signal processors (DSPs) or microcontrollers, to perform more complex signal processing tasks.
Another advantage of digital peak detectors is their ability to perform real-time peak detection. Since digital processing elements can process digital signals much faster than analog circuits can process analog signals, digital peak detectors can perform real-time peak detection with very high accuracy.
Here is a sample code for a digital peak detector in the C programming language:
#define ADC_SAMPLES 1024
int adc_values[ADC_SAMPLES]; // array to store ADC values
int peak_value = 0; // variable to store peak value
void setup() {
// initialize ADC and start conversion
analogReadResolution(12);
analogReadAveraging(32);
analogRead(A0);
}
void loop() {
// read ADC values and store them in the array
for (int i = 0; i < ADC_SAMPLES; i++) {
adc_values[i] = analogRead(A0);
}
// find the peak value in the ADC values array
for (int i = 0; i < ADC_SAMPLES; i++) {
if (adc_values[i] > peak_value) {
peak_value = adc_values[i];
}
}
// do something with the peak value
// ...
// reset peak value for next iteration
peak_value = 0;
}This code uses the ADC of an Arduino board to read the input signal and stores the ADC values in an array. The peak value is then found by iterating over the ADC values array and updating the peak_value variable whenever a new peak value is found. Finally, the peak value can be used for any desired purpose, such as displaying it on an LCD screen or transmitting it over a communication interface.
Analog peak detector
An analog peak detector is an electronic circuit used to detect and hold the peak value of an incoming analog signal. The circuit works by continuously monitoring the input signal and comparing it with a stored value (the current peak value). If the input signal exceeds the stored value, the circuit updates the stored value to the new peak value. This way, the circuit can continuously track and hold the highest amplitude of the input signal. Analog peak detectors are used in various applications such as radio communication systems, audio processing, and power supplies to detect and hold the maximum value of the input signal for further processing or analysis.
