Differential Amplifier Experiments

This is a follow-up to the Marantz 2240 Video. I didn't really do a very good job explaining the differential amplifier section and why I made some changes, including the addition of a constant Current Source. Hopefully this will give a demonstration of the diff amp and how it works with a resistor "tail" vs a CCS "tail". We also touch on how the feedback signal works in an amplifier.

Remember, there are many different ways to configure a differential amplifier. Additionally, there are many things that affect the performance of a diff pair including the characteristics of each transistor, temperature of the transistors, component accuracy, noise ingress/shielding and design variables.

In case you are interested, here are the actual values of some of the components used in the experiment:
Transistor 1: 2N2222, Vbe 626mV, Hfe 191
Transistor 2: 2N2222, Vbe 624mV, Hfe 193
Transistors were tested using one of those low cost component testers. I didn't do a proper curve trace or use my matching fixture.

Collector resistor 1: 10k ohms (actual resistance was 9755 ohms)
Collector resistor 2: 10k ohms (actual resistance was 9892 ohms)
Tail resistor: 5.6k (actual resistance was 5570 ohms)
CCS was a 2.5mA CCS