MOSFET help for 7segment PWM - Electronic Circuits Projects Diagrams Free

AHughes1984 · 10th June 2009, 05:00 PM

Hell all new here.

I am designing a seven segment LED clock (yes a clock again lol) but am stuck with a MOSFET. What it is, is that am using an UDN2981 (high side driver array) and will be using PWM on the 6 CA seven segments using the PWM pin of the PIC16F877. I will be PWM'ing the VCC pin of the UDN2981 With a MOSFET (12V connected to the source and the drain connected to the VCC pin with the gate connected to a BC847 with a 1K resistor). My problem is that am not sure which type of MOSFET to use ie n-channel or p-channel. I think i should be going for the p-channel and use a BC847 on the MOSFET gate whit the BC847 connected to the PIC's PWM pin. So could anyone tell me if my thinking here would work providing i select the correct resistors to saturate the BC847 (to use as a switch).

All so is the current flow in MOSFETS bi-directional.

Hope i have gave you all enough info.

Regards,
AHughes1984.

ella · 10th June 2009, 05:19 PM

Quote:

All so is the current flow in MOSFETS bi-directional.

No it depends on channel type n or p

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10th June 2009, 05:00 PM	#1
AHughes1984	MOSFET help for 7segment PWM Hell all new here. I am designing a seven segment LED clock (yes a clock again lol) but am stuck with a MOSFET. What it is, is that am using an UDN2981 (high side driver array) and will be using PWM on the 6 CA seven segments using the PWM pin of the PIC16F877. I will be PWM'ing the VCC pin of the UDN2981 With a MOSFET (12V connected to the source and the drain connected to the VCC pin with the gate connected to a BC847 with a 1K resistor). My problem is that am not sure which type of MOSFET to use ie n-channel or p-channel. I think i should be going for the p-channel and use a BC847 on the MOSFET gate whit the BC847 connected to the PIC's PWM pin. So could anyone tell me if my thinking here would work providing i select the correct resistors to saturate the BC847 (to use as a switch). All so is the current flow in MOSFETS bi-directional. Hope i have gave you all enough info. Regards, AHughes1984.