The frequency response of the above circuit is desired. For simplification, the voltage divider below can be ignored. When R2 is much larger than R1, the R2 resistor can be ignored as well. The hand calculations for the frequency response is as follows. Note that R2 is insignificant when R2>>R1 (because R1/R2 goes to zero).
The unity gain frequency of the circuit is calculated to be 159Hz, shown in the hand calculation and LTspice simulation below.
When building the circuit in lab, I only had access to a 5nF capacitor. The unity gain frequency of a similar circuit using C=5nF is 31.8kHz, shown in the hand calculation and LTspice simulation below:
The experimental results for the built circuit are as follows:
The image on the left includes the large R2 resistor, while the image on the right does not. This illustrates that the big R2 resistor does not have a significant impact on the frequency response of the circuit.
The image below was taken at the unity gain frequency. The input and output waveforms have an equal peak value.
Square-wave to Triangle-wave Generator
A square-wave to triangle-wave generator is desired with an input/output frequency of 10kHz and an output ramp swimg from 1V to 4V centered around 2.5V. The calculations are shown below:
The value for R is related to the other parameters by the formula: R=(1/C)*(1/Vout)*(Vin/2)*(T/2) where C is the capacitor value, Vout is the output ramp swing, Vin/2 is the half the amplitude of the square-wave function (which is also the difference between the peak Vin value and Vcm), and T is the period of the input and output. For this circuit, C=15nF and a Vin swing from 2.2V to 2.8V were chosen. Vout is required to be 3V and a frequency of 10kHz results in T=100us. Thus, a resistor value of 312.5 ohms is necessary. The LTspice schematic and simulation results are shown below:
The experimental results are below:
