I had to write it here because it is not a topic in the operational amplifiers section.
I am looking for a high speed opamp amplifier with fet input.
The ad820 provides 100 times the perfect gain, but instead of a different opamp compatible with the same place, I am thinking of a different series opamp in terms of price, it would be better if the gain was more than 100 times.
With 5v single source supply, but ad820 I could get good efficiency.
I shared the ad820 pictures I got from the genie, one of them is fake
It works fine which has data code 85604.
Can you recommend another opamp with rail output capabilities that does the same job as the AD820? High gain 5v single source application
I tried similar opams and got different results lm358,ad797,lm258,lm741. opa602.op27.opa637, ina118 vs. I tested it, the result was not good, it looks like it is designed for most double welders I need a different opinion I will wait for your suggestions thanks
So usually when selecting an op-amp you have some target specs in mind, like low offset voltage, low input bias, high slew rate etc. All you have really indicated is you want "high speed", (which the AD820 is not), high gain which comes with other considerations such as noise, offset voltage, and single supply.
We really can't help you much with that little information. Some application details would be helpful.
Given that none of the seemingly random op-amps you've plugged in are rail to rail, which the AD820 is, for all we know just another basic general purpose RRIO op-amp like the MCP6021 may be suitable. The AD820 has a max offset voltage of 800uV, the MCP6021 is a little better at maybe 500uV, but both those numbers are really high for a gain of 100. An OPA145 is maybe a better choice as a general purpose low noise op-amp with somewhat better 150uV offset voltage.
Based on what you've posted its really just a guess.
Describe your application, you may be in the wrong neighborhood with the AD820 already.
By itself an op-amp has very high "open loop" gain. So high that it's not usable as an amplifier without negative feedback (resistors) to control/define the gain. The resistor calculations "assume" infinite gain, and in the real world the accuracy of the gain depends on the precision/tolerance of the resistors.
You can look-up the circuit for inverting & non-inverting op-amps but your existing circuit might not be that simple.
...An op-amp without feedback can be used as a comparator where the "infinite" gain slams the output to the maximum positive output when the +input is higher (or more positive) than the -input, and when the -input is higher (or more positive) the output slams to the maximum negative output.
Op-amps are "widely interchangeable" but you want a FET input and maybe a rail-to-rail output.
Op-amps are usually low-power (low current) so "efficiency" isn't usually an issue unless maybe if your device is battery operated.
Actually I designed my clipboard to work both cif source and single source. I noticed unstable voltage movements on the pcb. Output gives 10mv and some 60mv.
Of course, I can compensate for this with the offset adjustment, but I wanted a stable voltage output.
Effects such as noise and lm2662 degradation will damage the negative voltage transient MCU. so i started testing for single source
The ina188 cif source worked more efficiently. I tried the instrumentation amplifier.
The voltage range I want to increase can be considered as dc voltage 500uv to 100mv max.
I'll take into account what you said, there are indeed many types of opamps and I should try the mcp 6021.
I tried another lm8261. mcp6001 has no bad gains either
Of course, you will ask how I tested them, you will ask.
I have a fixed heat source. I set 150 degrees to see 50 cm at max gain.
If the temperature is 1000 degrees, I will reduce the gain, if the same distance, this is enough for me
I bring it to reasonable levels as the gain is deducted manually
of course we can do this automatically with mcu codes
pcb fixed 24v DC-DC step-down 1cz41h 5v inverter I designed it runs mcu and opamps
For DC voltage in the 500uV - 100mV range a much simpler solution will be an ADS1115 set to Gain 16. It is linear and accurate over that entire range, and will be much simpler than trying to create this variable gain schematic you have proposed.
I have written articles on this subject before.
I have an application that will read ads1115 gain 200mv
The problem is that I can't compare the low voltages with the potentiometer.
I may have lowered the input voltage of the potentiometer, I fed it with 500mv, but I could not get 50cm output with the rotary encoder pot, maybe, but if I read 0.. 200mv or 0.5v, let me compare.
I couldn't start the tests. The rotor encoder was on my mind from the very beginning.
Both gain and rotor pot eeprom registration will be insufficient for the rotor. AT168 512 bytes .at328 1024 bytes
I haven't tried it with the map() function. 16 bits 32767 steps convert it to mv so
In any case, it will work as an amp that acts as a preamp for the input.
Previously, the current system was already working fine, I was using 10bit analog input.
then it took me a while to realize that there was insufficient resolution for distant materials
I continue with Ads1115. I need to redesign my usage card in the future.
15bit provided sufficient resolution
I share it with you, who have different experiences on this subject, so that it can be developed.
It's not clear to me from what you have posted what the purpose of the potentiometer is.
However, is there a good reason why you chose to amplify the temperature signal to operate the ADS1115 in the range of the potentiometer? I would consider using a high resistance value voltage divider to step down the potentiometer input to the 0-256mV range for the ADS1115 and eliminate the errors and complexity of amplifying the signal from the temperature input.
yes I'm trying.. I measured 0..256mv. I tried the potentiometer with a multi-turn potentiometer, not a single turn. The transitions between the O..256mv were better, but did not fit in the multi-turn crucible.
Pot input to 0.256mv. The 256 step eeprom can have a rotary encoder.
I'll listen to anyone who has different suggestions, thanks