Lab 4: Capacitive sensors and charge amplifier Consider a charge amplifier shown in the following figure. R1=100W, C1-1 nF, R2=1 GW, C2-10 pF. The op amp is AD795 and the power supply for AD795 is ± 10V. The capacitive sensor is modeled as a current source connected in parallel with a capacitor C1. C1 R1 w C2 HH R2 ww U1 (1) [30%] Simulate the offset voltage on the output for two cases: (1) without R2 and (2) with R2. Explain your simulation results with theoretical analysis. (2) [40%] Simulate (AC sweep) the gain as a function of frequency (from 1 Hz to 1 MHz). Note that this simulation is a little tricky since the input of the amplifier is charge DC, and the corresponding current, which can not be directly modelled in Multisim due to s. So we convert the current source to a voltage source by Thevenin theorem as shown in the figure on the next page. Now the voltage. Then we can use AC sweep to simulate Vo/Vi from 1 Hz to 1 MHz and then can be calculated by Compare your simulation result with analytical result. Discuss f and the gain in the signal band, but not fд. R2 PRZ R1 vss V1 C2 PR1 (3) Extra credit [10%]: in the class, we mentioned that. However, this f was calculated by assuming an ideal op amp or C1/C2 is very small. Now let's consider the finite open loop gain of op amp. Calculate the new fд and compare it with the simulation result. Hint: use the figure above, derive the voltage gain from the non-inverting terminal to the output in the pass band and then calculate the 3dB frequency based on the fact that the voltage gain x f3dB unity gain frequency. (4) [30%] Simulate the output noises due to R1 and R2 (from 1 Hz to 100 kHz). Compare simulation result with the analytical result.