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The currrent is supposed to flow into the base of the transistor. A base current of 20µA at hfe=270 will result in 5mA LED current.You will never get 20uA through there, since the 1M resistor will limit it to 3uA(@3V
The currrent is supposed to flow into the base of the transistor. A base current of 20µA at hfe=270 will result in 5mA LED current.
Putting the LED and current limiting resistor into the collector circuit could improve the circuit since the current source (photodiode) then sees only Vbe.
Harald
No, it is not a voltage generator. A photodiode generates a photocurrent. The voltage is only a consequence of the current flowing through a resistor (or in this case the LED and the base-emitter junction of the transistor).
I just wonder where you get the 20uA from in this circuit. What you say is like pulling yourself up with the hair, speaking in a metafor.
To model the photodiode you don't need the diode in the circuit. The current source alone is sufficient. The diode seems to irritate more than to help understanding the circuit.or in this case the Diode in parallel with the current source).
You can use the output of the transistor circuit as a control signal for an H-bridge. You cannot power the bridge from a photodiode.Where the H Bridge operates from the signals received from the IR Receiver