0
\$\begingroup\$

I have a question regarding the voltage specification of the TSH82 OpAmp: Datasheet.

In the data-sheet, maximum ratings I find (Table 1):

  • Vcc Supply Voltage 14V
  • Vid Differential Input Voltage ±2V
  • Vi Input Voltage ±6V

The common mode input voltage range on the other hand is defined as (Table 2): Vcc- to (Vcc+ -1.1). Note that the data-sheet of this part does not use the usual Vcc and Vdd nomenclature but uses Vcc- and Vcc+ instead.

Question:

If the common mode input voltage goes basically from negative supply to 1V below positive supply, what does the "Vi Input Voltage ±6V" from table 1 refer to? It seem to contradict with the common mode input voltage range because it's range is much lower when the device is powered from lets say 9V.

Reason I'm asking is, that I want to use one unit as a comparator (save space, reduce cost). Since it's not ideal to use an OpAmp as a comparator I really have to pay attention to these details.

\$\endgroup\$
  • \$\begingroup\$ check note (3) in that abs max table, against the Vi specification, then edit your question \$\endgroup\$ – Neil_UK Nov 15 '15 at 13:46
  • \$\begingroup\$ @user44635 That note(3) just specifies that you should not exceed Vcc+ by more than 0.3V. That's such a common restriction that I think it doesn't add much to the question. \$\endgroup\$ – Nils Pipenbrinck Nov 15 '15 at 14:01
  • \$\begingroup\$ vcc+0.3 is a common, but not ubiquitous restriction. When limiting the voltage on Vi, you should go by the most restrictive spec mentioned, the union of all allowable voltages, so the +/-6v only applies when you have a 12v rail. As Andy points out, vdiff will be the killer, unless you design your way round that. \$\endgroup\$ – Neil_UK Nov 15 '15 at 15:04
  • \$\begingroup\$ @user44635 Yep, I know. My differential voltage will be below 1V, so no problem. \$\endgroup\$ – Nils Pipenbrinck Nov 15 '15 at 15:07
1
\$\begingroup\$

To use it as a comparator be aware that the maximum voltage difference between the two inputs is 2V and this is usually a problem if using it as a comparator.

All restrictions apply equally but some only apply to certain scenarios. If the common mode range is +/- 6V and you are running from a supply that is +/- 5V then that restriction is defeated by the input common mode range being between -Vs and +Vs-1.1V.

If the supply is +/-6.5 volts then the input common mode range does NOT extend to -Vs any more.

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.