Derivative Receiver Amplifier (OPAMP) / The Differentiator Amplifier

In this article, we will discuss Derivative Receptor Amplifier (OPAMP) / The Differentiator Amplifier.

Here the position of the capacitor and resistance is reversed. Now the reassurance XC is connected to the inlet terminal of the inverter amplifier, while resistance Rε normally forms the negative feedback element along the operational amplifier.

This transactional amplifier circuit performs the mathematical operation of the differential. In other words, it "produces a voltage output that is directly proportional to the rate of change of the input voltage over time". In other words, the faster or larger the change in the input voltage signal, the greater the input current. So if the output voltage change is that big, it will cause more spikes in shape.

As with the integrator circuit, we have a resistance and capacitor that forms an RC Network along the transactional amplifier, and the capacitor's reassurance (Xc) plays an important role in the performance of an Op-amp Derivative Receiver.

Op-amp Derivative Receiver Circuit

Derivative Receiver Amplifier
Op-amp Differentiator Circuit

The capacitor blocks any DC content. Thus, there is no current flow to the amplifier collection point, X causes zero output voltage. The capacitor only allows AC type input voltage changes to pass, and its frequency depends on the speed of change of the input signal.

At low frequencies, the shutter is "High", resulting in low gain (Rε/Xc) and output voltage lower than op-amp. At higher frequencies, the shutter's reactance is much lower. This results in higher gain and higher output voltage from the Derivative Receiver riser.

However, at high frequencies, an op-amp Derivative Receiver circuit becomes unstable and begins to oscillate. This is mainly due to the first-degree effect of the op-amp circuit, which determines the frequency response of the op-amp circuit, which causes a circumstantial response that gives a much higher output voltage than expected at high frequencies. To prevent this, the high frequency gain of the circuit must be reduced by adding an additional small value capacitor to the feedback resistance Rε.

Okay, there's some math to explain what's going on! Since the node voltage in the inverted input terminal of the transactional amplifier is zero, the i current flowing from the capacitor will be given as follows:

Derivative Receiver Amplifier

The load on the capacitor is equal.

Derivative Receiver Amplifier

Thus, the rate at which this load changes:

Derivative Receiver Amplifier

however, dQ/dt is the capacitor current;

Derivative Receiver Amplifier

The equation with which we have an ideal voltage output for the Derivative Receiver op-amp is given as follows:

Derivative Receiver Amplifier

Therefore, the output voltage Vout is a variant of a fixed –Rε*C times input voltage relative to vin time. The minus sign (–) indicates a 180 degree phase shift because the input signal is connected to the inverted input terminal of the operational amplifier.

One last point to mention is that the Derivative Receiver Op-amp circuit in its basic format has two main drawbacks compared to the previous transactional amp integrator circuit. The first is that it suffers from instability at high frequencies, as mentioned above, while the other is that capacitive input makes it very sensitive to random noise signals, and any noise or harmonics in the welding circuit are raised more than the input signal itself. This is due to the fact that the output is proportional to the slope of the input voltage, so some ways of limiting bandwidth are needed to achieve closed loop stability.

Op-amp Derivative Receiver WaveForms

If we apply an ever-changing signal such as a square wave, triangle or sinus wave type signal to the input of the Derivative Receptor amplifier circuit, the resulting output signal will change and its final shape will depend on the RC time constant of resistance.

Derivative Receiver Amplifier
Op-amp derivative receiver WaveForms

Improved Op-amp Derivative Receiver Amplifier

The basic single resistance and single capacitor op-amp Derivative Receiver circuit are not widely used to rearrange the mathematical function of differentiation due to the two natural errors mentioned above, "Instability" and "Noise". Therefore, to reduce the overall closed loop gain of the circuit at high frequencies, an extra resistance to the input, Rin is added, as shown below.

Improved Op-amp Derivative Receiver Amplifier

Derivative Receiver Amplifier
Improved Op-amp Differentiator Amplifier

The addition of input resistance RIN limits the earnings increase of Derivative Buyers at Rε/RIN. The circuit now acts as a Derivative Receiver amplifier at low frequencies and a resistant feedback amplifier at high frequencies, providing much better noise cancellation.

Additional weakening of higher frequencies is carried out by connecting a capacitor Cε in parallel with the Derivative Transceiver feed resistance Rε. This then forms the basis of the Active High Pass Filter, as we have already seen in the filters section.