# Linear rectifier circuit

#### Pyrex

Joined Feb 16, 2022
262
Hi, colleagues

I want to built an ESR tester, powered from a 2.4V Ni-Mh battery ( 2xAAA). The moving coil meter, 200uA 500 Ohm to read the value will be used.
Stucked with the rectifier stage. I'd like to avoid using of a special Opamps or special ICs. Can anyone point me to a circuit diagram ? Accuracy of 5% is acceptable. The previous cascade impedance is 10 kOhm, maximum output is 100mV, frequency is 100 kHz.
Circuits from a college books is out of interest, I need a real circuit diagram...

#### AnalogKid

Joined Aug 1, 2013
11,021
2.4 V is not much to work with, but it can be done. Can the 100 kHz be a square wave, or must it be a sine wave?

ak

#### crutschow

Joined Mar 14, 2008
34,386
Show us your proposed circuit for the measurement.

#### schmitt trigger

Joined Jul 12, 2010
885
If you only have 2.4 volts which will drop to less than 2 as batteries deplete, a plain vainilla opamp won’t cut the mustard.

#### Pyrex

Joined Feb 16, 2022
262
2.4 V is not much to work with, but it can be done. Can the 100 kHz be a square wave, or must it be a sine wave?

ak
sine

#### sghioto

Joined Dec 31, 2017
5,388
I want to built an ESR tester, powered from a 2.4V Ni-Mh battery ( 2xAAA)
Does it have to be 2.4 volts? A lot of the circuits I have seen draw very little current and a 9 volt battery would suffice without taking up any additional space.

#### BobTPH

Joined Jun 5, 2013
8,921

#### AnalogKid

Joined Aug 1, 2013
11,021
Beat me to it while I was off banging on another thread.

ak

#### Pyrex

Joined Feb 16, 2022
262

#### Pyrex

Joined Feb 16, 2022
262
Show us your proposed circuit for the measurement.
Nothing special:

Sine w oscillator --- Cx----Amplifier-----Linear rectifier-----200uA meter

#### AnalogKid

Joined Aug 1, 2013
11,021
What do you mean by "linear rectifier"?

ak

#### schmitt trigger

Joined Jul 12, 2010
885
I believe he means “precision rectifier”.
But that is only my guess.

#### Pyrex

Joined Feb 16, 2022
262

#### Alec_t

Joined Sep 17, 2013
14,310
If you've only got a 2.4V supply I'd be interested to see if anyone could could come up with a precision rectifier with 5% (or even 10%) accuracy. Even Schottky diodes would eat into that voltage allowance.

#### Pyrex

Joined Feb 16, 2022
262
If you've only got a 2.4V supply I'd be interested to see if anyone could could come up with a precision rectifier with 5% (or even 10%) accuracy. Even Schottky diodes would eat into that voltage allowance.
No problem . I have some HF germanium transistors and small signal germanium diodes.
Some time ago I saw an ESR meter powered from a 1,5V battery on a forum. It was crystalradio.cn link , I guess. Sorry, can't find the circuit diagram at the moment

#### Hymie

Joined Mar 30, 2018
1,282
If the op-amp is notionally operating at unity gain (with the feedback), and you want a voltage output swing of less than +1V then an op-amp with a 1MHz bandwidth should easily do the job. There are a number of fairly inexpensive op-amps with a 1MHz bandwidth – but I’d recommend you test the circuit design using LTspice.

#### Pyrex

Joined Feb 16, 2022
262
If the op-amp is notionally operating at unity gain (with the feedback), and you want a voltage output swing of less than +1V then an op-amp with a 1MHz bandwidth should easily do the job. There are a number of fairly inexpensive op-amps with a 1MHz bandwidth – but I’d recommend you test the circuit design using LTspice.
Really ? A quite fast opamp OPA2211 ( slew ratio is 27 V/us , unity gain BW is 45 MHz), shows a clearly visible distortions at 100kHz :

Precision Full-Wave Rectifier, Dual-Supply

#### AnalogKid

Joined Aug 1, 2013
11,021
A quite fast opamp OPA2211 ( slew ratio is 27 V/us , unity gain BW is 45 MHz), shows a clearly visible distortions at 100kHz :

Precision Full-Wave Rectifier, Dual-Supply
Please indicate the figure or paragraph you are referencing.

If the author had run multiple generations of opamps through the same circuit, you might find that the distortions have more to do with the device's internal topology than simply its bandwidth. IOW, I wonder how an LM318 from the 1970's would perform at 50 kHz. Same for a current-feedback opamp from the 1990's.

Also, don't confuse simulation results with the real world. TI knows a lot about modelling, but I wouldn't trust anyone's models when chasing this kind of subtlety.

BTW, nice find on the article.

ak

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#### Hymie

Joined Mar 30, 2018
1,282
A little while back I was experimenting with an LT1361 dual op-amp with a 50MHz bandwidth. Although having a maximum 36V rail, there is no way that the device can output a sine wave with peak to peak (0-36V) even at 10MHz unity gain.

The datasheet shows the undistorted output voltage swing limited to 10V (p-p) at around 5MHz. But I would be very surprised if the LT1361 would not be suitable in your application. I think I purchased 5 for around \$15 including p&p from an ebay seller.