Matching transistors for discrete opamp (audio use)
Your test setup is basically a follower, which tends to reduce the effects of gain spreads. While this is good in production, it's not what's wanted here. In your job, the idle current is known, so you can set up a common emitter stage to pull the idle current. Also, the \$V_{CE}\$ the discrete op amp provides to the transistors can be determined. So you are setting up your test transistor under the same DC conditions that it will see in the discrete op amp. Now use a standard common emitter circuit with NO negative feedback. This implies using a fully bypassed emitter resistor. Now you will see more variability when you feed in your AC from your signal generator. Picking a pair will now be clear.