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Comparator as operational amplifier

The response is going to be dominated by the output load capacitance. The equivalent overall gm is going to be very high. Analyzing that will be nigh on impossible. Experiment and pray ;-) ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson
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 Thanks, 
    - Win
Reply to
Winfield Hill

the output within 1 us

ht I could trick that comparator into changing gender to a opamp

y links can be shared)

e amplified 15 times, hence the resistive divider

U3 is closed. So the RC filter R4 and C3 oscillates around the output volta ge of 3V. The RC ramp is set so the output will ramp up in about 300ns.

lot of ripple. Then, the switch is opened up, and the ripple is now low sin

that allows the output to settle to the correct value before the ADC is tri ggered

Dunno if anyone suggested it, but maybe use a dual, quad, whatever fast OA and make a comparator out of one of those, since we know it's rather straig htforward to configure an OA as a comparator.

Reply to
bloggs.fredbloggs.fred

But try it first. Some opamps do nasty things if run open-loop and railed, the easy way to make a comparator.

Some duals and quads will mess up all the amps if one is used as a railing comparator.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

s the output within 1 us

ught I could trick that comparator into changing gender to a opamp

way links can be shared)

ave amplified 15 times, hence the resistive divider

h U3 is closed. So the RC filter R4 and C3 oscillates around the output vol tage of 3V. The RC ramp is set so the output will ramp up in about 300ns.

a lot of ripple. Then, the switch is opened up, and the ripple is now low s

t that allows the output to settle to the correct value before the ADC is t riggered

A and make a comparator out of one of those, since we know it's rather stra ightforward to configure an OA as a comparator.

The comparator is actually a spare device inside a microcontroller, so it's not possible to get a quad

Cheers

Klaus

Reply to
Klaus Kragelund

les the output within 1 us

hought I could trick that comparator into changing gender to a opamp

e way links can be shared)

have amplified 15 times, hence the resistive divider

tch U3 is closed. So the RC filter R4 and C3 oscillates around the output v oltage of 3V. The RC ramp is set so the output will ramp up in about 300ns.

h a lot of ripple. Then, the switch is opened up, and the ripple is now low

but that allows the output to settle to the correct value before the ADC is triggered

OA and make a comparator out of one of those, since we know it's rather st raightforward to configure an OA as a comparator.

's not possible to get a quad

If it's CMOS then keeping those inputs linear is a quick way to turn u- or n-Amps quiescent into milliamps. Have you tried it yet?

Reply to
bloggs.fredbloggs.fred

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