Diff amp with 100pF C-B cap and current source tail PUBLIC

Not provided.

Differential amplifier with current source and capacitors from collector to base to reduce high frequency gain.

Observations:

1 The common mode gain increases with frequency. At 1KHZ, the common mode gain with 100pF capacitors increases by $\approx$ $\times10$ compared with no collector to base capacitors. There is also a phase shift of $\approx 90^o$. As the frequency is decreased to 1HZ, the common mode gain becomes really low, implying the current source resistance is $\gt$ 50M$\Omega$. Also the output is in phase with input.

2 At 1KHZ, the differential gain with 100pF capacitors is 36, compared to the expected 37.5.At 100KHZ the differential gain drops to 31 with the 100pF caps.