About the "Improved Peak Detector" available here:
Demo Circuit: https://www.analog.com/media/en/simulation-models/LTspice-demo-circuits/LTC6244_PeakDetector_Improved.asc
I would like to measure the DC with an voltmeter, so the holding time must be, at least, 3~5 seconds, and the LTSpice show me a holding time of only 1~2 ms.
I tried increase the capacitor (C1) value, as well R4 and R6, but with no success.
May someone give me a help about how to increase the holding time to 3~5 seconds?
Thanks in advance,
3-5 seconds is a very long time for any sample-hold circuit. One thing you could do is replace R4 with a low-leakage analog switch (or JFET), which you could use to reset C1 to zero, then open to capture a new peak value.
But D2 reverse leakage would be a problem - you could replace D2 and D3 with a diode-connected JFETs. This may reduce the accuracy, and you would want to match the forward drops of D2 and D3 accordingly.
Another point - does your end application really using a handheld voltmeter, or is this an intermediate step in your development, to eventually be replaced with an integrated circuit ADC, with data either being displayed, or captured by a host computer? If the latter, consider skipping the voltmeter, and use a low-cost microcontroller platform that has an onboard ADC for this step. Even an Arduino Uno might do the job, you could use it to control the reset / capture operation of the circuit, digitize the sample-hold output, and display either to a computer connected via USB serial port, or to an LCD screen.
This might be a good starting point:
Thank you for your support!
I was thinking to use it with a handheld voltmeter.
Now, with your suggestion, I will use arduino to storage the peaks in a SD Card and show the max value in a LCD screen.