OPA2156: Can OPA2156 be a comparator?

Roy Chou1

Part Number: OPA2156
Other Parts Discussed in Thread: OPA2192, , TLE2142, OPA828

Hi Team,

We used OPA2192 and OPA 2156 as comparator, but the OPA2156 behavior is wrong when we input the INA signal. It looks like that the OPA2156 output is short so that INA current is large and output voltage is getting small. I'm not sure why OPA2156 can't be a comparator.

Regards,

Roy

over 2 years ago

0 kai klaas69 over 2 years ago

Guru 140200 points

Hi Roy,

according to section 6.1 and 7.2 of datasheet the OPA2156 has protection diodes between the inputs. So the OPA2156 cannot be used as comparator.

Kai

0 Thomas Kuehl over 2 years ago

TI__Guru* 93105 points

Hi Roy,

Kai is completely correct regarding the OPA2156 having input clamp diodes which precludes it being used for most comparator applications. The exception is when the voltage difference between the two OPA2156 inputs is kept well below the forward turn-on voltages of the back-to-back input clamp diodes (< a few hundred millivolts), and operated within the linear common-mode voltage range.

The OPA2192 does not use input clamp diodes so that allows it to be more readily usable as a full input range comparator. Additionally, it has rail-to-rail input and output voltage ranges and a fast output overload recovery time. It makes for a good, moderately fast comparator.

Regards, Thomas

Precision Amplifiers Applications Engineering

0 Roy Chou1 over 2 years ago in reply to Thomas Kuehl

TI__Genius 12635 points

Hi Thomas and Kai,

Thanks for information. May you let me know if there is solution that P2P compatible with OPA2192 but higher slew rate like 40V/us?

If there is no appropriate P2P device, may you suggest me the non-P2P device but higher slew rate.

Roy

0 kai klaas69 over 2 years ago in reply to Roy Chou1

Guru 140200 points

Hi Roy,

what supply voltage do you need?

Kai

0 Roy Chou1 over 2 years ago in reply to kai klaas69

TI__Genius 12635 points

Kai,

Vcc should be +27V. I find TLC214x, but Vcc is only support to 22V

Roy

0 Marek Lis over 2 years ago in reply to Roy Chou1

TI__Guru 60610 points

Dual TLE2142 typical slew rate meets your min 40V/us requirement but OPA828 single with 150V/us slew would be a better choice.

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OPA2156: Can OPA2156 be a comparator?