|Jul16-11, 10:09 AM||#1|
Switching/circuit breaker circuits
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.
|Jul16-11, 12:33 PM||#2|
The simplest type of switch just uses a single MOSFET - when you apply a gate voltage above the threshold, it has a very small resistance between source and drain. When you apply zero volts, it has a higher resistance.
One can then build more complex circuits uses multiple transistors to give a lower on-resistance and higher off-resistance, but at the cost of a slower response.
|Jul18-11, 02:40 AM||#3|
Thanks very much for your reply!
Current rating would be from 40 mA to 150 mA.
Do you have any reference circuits or model that will feed into this applications? I need to a circuit to start with. Thank you.
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