Other Parts Discussed in Thread: BUF634A,
The objective is to use the BUF634A as a high output current buffer for a digital-to-analog converter with limited current drive. The issue, circuit can become unstable when driving 250Ohm resistive heaters with the BUF634ADEVM board.
Configuration:
a) Board powered with +/-8V.
b) Load is resistive 250 to 350 Ohms
c) Input voltage range is 0 - 5volts, DC to 100Hz.
The following board modification were made,
1) Changed R7 and R8 to zero ohm so output directly drives load resistance.
2) Removed R12 and R13 to reduce bandwidth (after observing instability).
Behavior - Circuit operates normally much of time but occasionally become unstable. When unstable the supply current is abnormally high and the outputs no longer following the input. Normally the positive supply current draw is as expected for a given input voltage and the negative supply current draw in nearly zero amps. When operating abnormally the current draw on both rails is approximately equal and abnormally high. Power has to be shutdown to reset the instablity.
Parts are on order to add a feedback loop using U1.
Can you comment on the arrangement and if this instability is expected when directly driving resistive loads > 250Ohms? If expected, or not surprising, what are recommended corrective actions.
Thank you.
