voltage transfer circuit

[balutan]

Noob question.
Referring to the circuit attached, what is the purpose of having R276 between the gate and source of the transistor?
This is a typical voltage transfer circuit from microprocessor signal "TXDSNMP" (3.3V/0V) to "SNMPTXD" (+12V/-12V) signal. Thanks in advance.

 

[itsmoked]

To assure that Q6 is OFF. If whatever is driving TXDSNMP has some leakage current, that resistor is to shunt it to ground and not allow it to charge the gate up to turn-ON.

Most processors that would be hooked that pin cold boot to INPUT. That would have two inputs connected while the CPU initializes - a second reason for R276.

Keith Cress
kcress -

http://www.flaminsystems.com