LT1819 not responding

Hi,

Is it possible for you to post your schematic?
It would help us to check other possible components that may cause the issue.

Thanks and regards!

Hi,

Which LT1819 is not working from your circuit?
What is your expected voltage level in each output of LT1819?

Also, I can see that you are using -3V/5V supply to your LT1819.
From your previous query, you have mentioned -3V/9V voltage supply.

Thanks and regards.

Hi   I have tried -3V to 9V. but it is not working. opamp heating issue is there. so I tried to use 0 to 5 v. out actual opamp output expectation is 0 to 4.096V only

both opamp stage is not working. both are same IC

Hello,

The part was specified at +/-5V (10V).
We can guarantee device performance using this supply range.

Using supply of -3V to 9V means 12V supply range.
The device Absolute Maximum Rating is 12.6V.
Any overshoot on your voltage supply will possible hit and violate Abs Max Rating.

Hence, the PSRR of the part is tested up to 11V only.

Can you do a diode check on the LT1819 pins?
This to check for any shorted pins.

Thanks and regards!

Hi There is no short in pins. I have tested with 0 to 5V. but here output is varying continuously

200-300mV

Hi,

I'm not sure how will you have 4.096V as an output.

Based from your circuit, the output of the LT6275 is 0.00004 * 4.7k = 188mV.
The output of the U1 LT1819 = 188mV [1 + (1.33k/50k)] = 193mV.
The output of U2 LT1819 = 193mV [10k / (5k + 10k)] = 129mV.

That is the expected output based from your circuit.

Thanks and regards!

Hi,

I'm not sure how will you have 4.096V as an output.

Based from your circuit, the output of the LT6275 is 0.00004 * 4.7k = 188mV.
The output of the U1 LT1819 = 188mV [1 + (1.33k/50k)] = 193mV.
The output of U2 LT1819 = 193mV [10k / (5k + 10k)] = 129mV.

That is the expected output based from your circuit.

Thanks and regards!

Correct. am sweeping input current from LT6275 from 0.04mA to 1.2mA

am getting some output but it is toggle - 200 to 500mV noise is there

Hi,

When using single supply of 5V/GND, your minimum input is limited to 1.5V and 800mV typical.
Thus, the part will not accept input lower than this values.

I suggest you pick op-amps with rail-to-rail input and rail-to-rail output.
Else, use a split supply with 10V range (e.g. -3.5/+6.5V).

Thanks and regards!

Hi If I try negative voltage opamp got heated

even if I give -1V also it is heating. can you suggest any

Hello,

Do you mean negative voltage at the supply?
This should not be an issue.

If using single supply(e.g. 5V/GND), does your part heats up?

I think your part might be already damaged.

Thanks and regards!

Single 0 to 5v it is not heating. If I change negative supply it is heating

Single supply is working good. But output range is 0.5 to 4.5v. I need 0- 4.5 v

Hi,

Can you try 10V/GND on your supply and check if there is a heating issue.

Thanks and regards!

Not heating for 0 to 9V

Hi,

Since you are also seeing oscillation as you have mentioned (-200mV to 500mV), please consider using feedback capacitor along with your feedback resistor (R3) at U1.
The Cf value is obtained by the equation: CF > RG • CIN/RF

Also, the U2 is driving 10nF Cap load.
Please use isolation resistor value of 10 to 50 ohms as recommended by the data sheet.

And the least thing, if you are open on using fresh unit to check if you will have the same performance as what you have now.
In addition, please use supply voltage of 10V only.

Thanks and regards!