What is the function of R1 in the circuit in the figure?

kal9623287

What is the function of R1 in the circuit in the figure? [Copy link]

As the title says, what is the function of R1 in the circuit in the figure?

maychang

R1 is connected in parallel across the emitter junction of T1 to shunt the base current of T1, thus preventing the collector-emitter leakage current of T1 from causing current to flow through T2 when the base current of T1 is zero.

chunyang

Another point of view: R1 is a static bias resistor. When the input at the lower end of R2 is floating or the output of the previous signal source is high and the internal resistance is large, it can ensure that T1 is in the cut-off state. Its meaning is as mentioned above. If the front-end output is guaranteed not to float or have a high internal resistance (for example, the front-end is a push-pull output), R1 can be omitted.

alan_w02

Bias resistor for transistor B

elec921

Fixed B-pole potential can be understood as having the same function as a pull-up resistor

Fred_1977

The main purpose is to provide a bias voltage for T1 to ensure that T1 works stably and reliably.