TLV8542: Output Impedance for Unbiased State

Jejomar Ildefonso

Part Number: TLV8542

Hi Team,

What is the output impedance of the TLV8542 amplifier in an unbiased state?

Asking this question as our customer is using the op-amp in driving the control signal of a switch. In a later state, the bias of the op-amp will be removed (turning it off) but the output will still be connected to a different stage in that certain state. With this we need to know if the output of the op-amp will exhibit a high impedance (which is desired) or if they have to use some kind of diode isolation (but would prefer not to).

To put it simply, the control signaling of the switch is still active, but will be driven from a different source than the TLV8542.

Thanks in advance!

Kind Regards,

Jejomar

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Jejomar,

driving the output of an unpowered OPAmp is never a good idea. An additional diode with a low ohmic resistor to shunt the leakage current to signal ground seems to be a good remedy here.

Kai

0 Ron Michallick over 4 years ago in reply to kai klaas69

TI__Guru**** 165376 points

Hello Jejomar,

Most op amps including TLV8542 have a 'diode' to power supply pins. Therefore voltage greater than +/-300mV will create a current path at the output pin. The output is only Hi-Z for very low voltage. The output is not designed for the external current flow.

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TLV8542: Output Impedance for Unbiased State