Discrete Schmitt Trigger

This is a schmitt trigger circuit. This circuit produces a simple comparator action. It is “emitter coupled”. This circuit has a distinct hysteresis loop and fast transition action because this circuit uses the 2N3565 bipolar that is a high hFE transistor. The 2N3069 JFET generates very little loading on the measured input. Here is the circuit :

[Source: National Semiconductor Application Note]