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how to increase photodarlington voltage?

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4tuty

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I used 100 ohms accross the photo darlington and the voltage obtained from it is 360mv i need 3volts to give input to AD630 for lockin amplifier application.

inorder to increase the voltage shall i use INA 121P of 10 gain? or 100 gain or 1000gain .

i need a circuit to choose the resistor value
 

Hi,

i wonder how you come to gain of 10 / 100 / 1000?
--> 3V / 360mV = 8.33

Why INA? A simple noninverting OPAMP circuit is OK.

But as Frank wrote: a schematic could help. And the informations where you measure the 360V and the 3V ...

Klaus
 

100 ohms seems too low, can you give us your circuit and some sort of specification, i.e. frequency response?
Frank

So for what i did is shown in page 1:cry:. i am planning to do lockin amplifier circuit is in page 2:idea:.

please correct my mistakes regarding resistor and capacitor values:thumbsup:

any other suggestions are welcome and appreciated:


i use Multimeter to measure the 340mV
50% duty cycle i used
 

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What is the pull up resistor and voltage coming back down the line from the lock in amplifier? To get the maximum voltage change from the photo darlington, earth the emitter and connect the collector to a +Vcc via a high value resistor.
Frank
 

Hi,

So for what i did is shown in page 1.
Page1: Your connection of photodiode in series with 100R then input to lockin makes no sense.

Klaus
 

A more reasonable circuit has been posted in your other thread https://www.edaboard.com/threads/343922/

photo-darlington.png

I think, this parallel discussion should be stopped.
 

If you get 360mV across your 100 ohms, then the current through it is .36/100 = 3.6 mA. If this current flows through a 10 K resistor then the voltage drop across it will about 4.8V. As I said earth the emitter and return the collector to the +5V rail via a 10K and take the output from the collector.
Frank
 
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