irf630 alternative

Audioguru

Joined Dec 20, 2007
11,248
The circuit does not have an LED so it doesn't show a current-limiting resistor for an LED.
a current-limiting resistor must be in series with each LED.
 

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markosillypig

Joined Jul 21, 2008
188
hi all again
this circuit works fine but i was just wondering what the r2 100k has to do with this circuit as i have removed it and it does not make a difference??
and finaly i would like to increase the output voltage to the led would it be possible to do this via a 2n7000 from the vcc+ to the 2.7v output and then to the anode many thanks all
 

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SgtWookie

Joined Jul 17, 2007
22,230
hi all again
this circuit works fine but i was just wondering what the r2 100k has to do with this circuit as i have removed it and it does not make a difference??
R2 ensures that the input is pulled to ground if there is nothing connected. This is in keeping with good design practice when using 4000 series CMOS IC's; you must never leave an input floating. In the absence of an input signal, R2 would pull the input to ground.
and finally I would like to increase the output voltage to the led.
The reason the voltage to the LED is so low is that 4000 series CMOS logic ICs have very low source/sink current capability.

Would it be possible to do this via a 2n7000 from the vcc+ to the 2.7v output and then to the anode?l
Connect: a suitable resistor to limit current through the LED to Vcc. To calculate this value:
Rlimit >= (VoltageSource - VfLED) / DesiredLEDCurrent
Example: if you are using a red LED that is rated for 1.7Vf @ 15mA, and VoltageSource = 5V, then:
Rlimit = (5V - 1.7V) / 15mA = 3.3V / 0.015A = 220 Ohms, which is a standard value.
Connect: the anode (long lead) of the LED to the other end of the resistor.
Connect: the drain of the 2N7000 to the cathode (short lead) of the LED.
Connect: the gate of the 2N7000 to pin 12 or 13 using a 100 Ohm resistor.
Connect: the gate of the 2N7000 to the source using a 10k Ohm resistor. This ensures that the gate will be turned off if the IC is removed.
Connect: the source of the 2N7000 to ground.
 
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