Differential Input Clamps-- can they affect your op amp circuits?

RE: Differential Input Clamps-- can they affect your op amp circuits?

Kris Paxton — Tue, 28 Nov 2017 00:23:01 GMT

Hi Bruce,

I have an OPA241 op-amp current source (2-wire) where it looks like inputs are conducting.

When "latched-up", I see the following (approximately, relative to current-source - terminal):

V(+supply) = 5.74

V(+ input) = 2.35

V(-input) = 3.00

V(- supply) = 3.00

V(output) = 3.00

V(+input) should be 2.00V (200uA reference current into 10k) but the op-amp inputs seem to be conducting about 35uA through the differential inputs (- to +) into my 10k resistor.

1. Does OPA241 have input clamps?

If so, I need a similarly low-quiescent current, low offset (as low as available) single op-amp that can operate low voltage (as low as possible) without the clamps.

What about LMC6061? Does it have input clamps?

LMC6041 data sheet says "insensitivity to latch-up" ... is that referring to input clamps conducting?

Which TI op-amps do not have the clamps? Is there a list? A parameter search?

I can send you my circuit schematic.

RE: Differential Input Clamps-- can they affect your op amp circuits?

Bruce Trump — Mon, 18 Feb 2013 23:29:31 GMT

Steffen-- Could I ask you to please post this question on our E2E forum? Your question is not directly related to the topic this blog and could result in multiple posts to select the best op amp for your application. Here is the link to the precision amplifier forum...

e2e.ti.com/.../default.aspx

Regards-- Bruce

RE: Differential Input Clamps-- can they affect your op amp circuits?

Steffen — Mon, 18 Feb 2013 20:49:04 GMT

Hello Bruce,

I have a similar application like the one described in figure 3. Is there an alternative to the OPA140 with an increased Common-Mode Voltage Range? My supply voltage is +-12V, and according to the data sheet the upper limit of the Common-Mode Voltage Range of the OPA140 is (V+)–3.5. The input signal to the voltage follower in my application is +-10V.

Regards,

Steffen