So what exactly is an Op Amp shutdown pin supposed to do?

RE: So what exactly is an Op Amp shutdown pin supposed to do?

Thomas Kuehl — Fri, 13 Oct 2017 21:08:14 GMT

Hi Randy,

Actually, the shutdown feature is a popular feature for amplifiers that provide the capability. Indeed a bipolar or FET series switch in the power supply line can be used to shut down one, or more amplifiers. However, the switch circuit does require additional components which add cost, and those components do take up board space. The latter is often that is an important consideration; especially in portable electronics.

Other, maybe not so obvious benefits of the internal shutdown is enable/shutdown pin readily interfaces with standard logic voltage levels and its turn-on and turn-off times are characterized and provided in the datasheet. Additionally, some amplifiers having internal shutdown have an output circuit that appears as a very high impedance during shutdown which makes them usable in simple, multiplexer applications. These capabilities are sometimes important in applications and can ease the design effort. Those behaviors may not be so easily achieved with a series switch design. For an external shutdown the responsibility for those characteristics would likely fall on the circuit designer.

Regards, Thomas

RE: So what exactly is an Op Amp shutdown pin supposed to do?

Randy Madsen — Thu, 05 Oct 2017 20:47:13 GMT

So I am admittedly not smart when it comes to analog design... wondering why you wouldn't simply power cycle an opamp with a fet or something of that nature vs. using the shutdown line. Is that an attempt to reduce the number of parts you are using in a circuit? I for example have a circuit that I want to duty cycle the whole circuit so this enable/shutdown line doesn't seem helpful. Just looking for a comparison between the two methods.

RE: So what exactly is an Op Amp shutdown pin supposed to do?

Thomas Kuehl — Mon, 05 May 2014 18:45:32 GMT

Hello Hugh,

Yes, for the amplifier types you mention the operating current level is adjustable allowing one to limit the current to no more than is necessary to attain the required ac bandwidth. Some examples of such amplifiers are the LPV531 CMOS op amp, and the BUF634 hi-speed, high current buffer. Their amplifier functions can't be shut down completely.

Thank you for reading and your constructive comment.

Regards, Thomas

RE: So what exactly is an Op Amp shutdown pin supposed to do?

Hugh Montgomery — Mon, 05 May 2014 16:07:36 GMT

Some op amps were also programmable, which allowed you to set the quiescent current. Or you could use it similar to a shutdown pin and vary the quiescent current in a variety of ways. Changing the operating current affects the speed of the part.