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# Switching/circuit breaker circuits

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#### thavamaran

##### Member level 4
Hi guys, Im Thava. Im working in optical communication. Currently I want to design a circuit to turn of couple of inputs to my laser.

Say I have a supply of 5V to two pins of the laser, anode and cathode (pin 1 and pin 2). And then a bias current to another pin (pin 3).

At some interval of time, I want to switch off the 5 V input to cathode and of course anode is grounded; also switch off the input bias current.

The switching off time should be in about 100 kHz, and it should be controllable. It should be in a way that, if I supply a pulse with pulsewidth of 100 kHz, it should switch off exactly at the falling edge of the 100 kHz. Is it possible?

And the switching time should vary, like I can always change the switching time.

I just need some suggestions, ideas and discussion. I have so many ideas on doing it, but cant choose a proper way, so I just need some guidance. It will be much appreciated!! Thank you.

1. If you supply your "bias" from the cathode, switching off the cathode voltage removes the bias.
You don't say what current you are supplying the cathode, but in any case a transistor in series with it and the actual power supply will do the job.
From what you say, I am led to believe that you want to pulse your laser on and off at the rate of 100KHz (5 microsecs on, 5 microsecs off), this is a square wave. If you want to keep the "on" time the same, and have a longer off time then you need one timer to set the 5 micro secs ans another to set the off time. Or you can just use the square wave (50% on, 50% off) and alter its basic frequency, say from 10KHz to 500KHz. Specify what you want and some one here will sort it out for you.
Frank

My "bias" has different input and the cathode has different. The cathode have to be supplied at 2.5 V, the "bias" should be supplied between 40 mA to 120 mA.

The 100 kHz is only the pulsewidth, and not period. It should one time switching. Once the rise time comes, should be switched on and fall time should be switched off forever unless another rise time comes.

This all I want. Switching with respect to the pulsewidth. Pulsewidth could be maximum of 100 kHz and minimum of no idea, could be very small.

Thanks again.

Hi guys, can anyone suggest a switch that works similarly like CD4016 IC (Quad Bilateral Switch for Analog & digital signal) that operates for signal minimum of 3 GHz. Cause this switch only operates at MHz range. Please someone. Thank you. Attached is datasheet for the switch.

#### Attachments

• electrical switch CMOs.pdf
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