rajaram04
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Gain is not dependent on supply voltage but the 741 may not function properly with only 6V or 9V supply. Also a 10M feedback resistor may be too high to provide enough feedback current for this very old bipolar op-amp.
Brian.
As it is shown, the gain cannot be calculated. The output at pin 6 depends on what you are feeding into the non-inverting input just as much as it depends on the voltage from the photodiode. Obviously it is amplifying and I suspect if it isn't going unstable the gain is very high. Be aware that the bandwidth of a 741 in this configuration will be very narrow, maybe only a few KHz so if you are using it for IR commuication the output waveform will be extremely distorted.
Brian.
The circuit is sketched incorrectly or at least incomplete because the N.I. OP input is unconnected. At present, even the photo diode operation mode can't be clearly determined.
I would expect that the circuit is intended as I/V converter (transimpedance amplifier) with zero photo diode bias. In this case, a 741 would need a bipolar power supply or the photo diode and N.I. input must be connected to a virtual ground.
Typical 741 input bias current is 80 nA, in this case the circuit can possibly work with a 10M resistor.
That's why they are called photo-diodes, they respond to light!
If you want it to respond only to IR you have to use a type with a built in filter or provide one outside the diode to block other wavelengths.
Brian.
It depends what you are trying to achieve. If this is for responding to an IR remote control unit you need much wider bandwidth and there are specialized circuits that would be easier to use than a 741. If you are trying to measure the amount of IR light (a light level meter) you CAN use the 741 but better alternatives are available.
To filter out visible light you need a window that only passes IR wavelengths, you can buy IR filters (they look like black plastic) or a cheap source is from older TV/VCR remote control units. Many had a plastic window in them that looks deep red or violet when you shine white light through them. They are not as good as proper IR filters but they will block most of the visible light. You can put more than one of these windows in front of each other to get better filtering.
Brian.
It depends what you are trying to achieve. If this is for responding to an IR remote control unit you need much wider bandwidth and there are specialized circuits that would be easier to use than a 741. If you are trying to measure the amount of IR light (a light level meter) you CAN use the 741 but better alternatives are available.
To filter out visible light you need a window that only passes IR wavelengths, you can buy IR filters (they look like black plastic) or a cheap source is from older TV/VCR remote control units. Many had a plastic window in them that looks deep red or violet when you shine white light through them. They are not as good as proper IR filters but they will block most of the visible light. You can put more than one of these windows in front of each other to get better filtering.
Brian.