====== Multistage amplifier compensation ======
{{:courses:ec330:highgainamp1.png?300}}

Determine the gain of the amplifier in (a) when the transconductance of the inverter tends to infinity. 
Build the amplifier in (a) with an ideal gain of 2 and R<sub>1</sub> in 5kΩ to 10kΩ range. Use a 6V supply for this experiment. Measure the gain error. **Connect inputs of unused inverters to ground**

Apply a (small) squarewave and measure the step response. Is there an overshoot/ringing? 

{{:courses:ec330:highgainamp3a.png?400}}

The gain error can be reduced by increasing the loop gain. Use another inverter in cascade (and a unity gain inverter for negative feedback) as shown above and measure the circuit. Does it result in a better amplifier? Apply a (small) squarewave and measure the step response. Is there an overshoot/ringing? 

{{:courses:ec330:highgainamp3b.png?400}}

Compensate the amplifier by connecting a capacitor C<sub>1</sub> to ground as shown above. Adjust its value for 10% overshoot. Use a 100mVpp square wave input for this measurement. While choosing the compensation capacitor, start from small values, of the order of 100pF. 

{{:courses:ec330:highgainamp3c.png?400}}

Compensate the amplifier by connecting a capacitor C<sub>2</sub> across the second stage as shown above. Adjust its value for 10% overshoot. Comment on the compensation capacitor values C<sub>1</sub> and C<sub>2</sub> in the two cases. While choosing the compensation capacitor, start from small values, of the order of 100pF.