UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Biggles · 16th Feb 2019, 9:50 pm

Most of the VHF front end circuits I have seen in the past (they may be different now) have the source strapped directly to 0 volts and the input tuned circuit directly between the g1 connection and 0 volts, indicating zero bias on g1. However the g2 connection always seems to have some bias on it provided by a resistive potential divider between +ve and 0 volts. Presumably the device is using g2 to provide bias in enhancement mode. To be honest I have never experimented much with these devices. It was always change them if suspect, when I used to repair receivers as a job. They actually rarely gave trouble.
Alan.

16th Feb 2019, 9:50 pm	#13
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Testing a dual gate mosfet Most of the VHF front end circuits I have seen in the past (they may be different now) have the source strapped directly to 0 volts and the input tuned circuit directly between the g1 connection and 0 volts, indicating zero bias on g1. However the g2 connection always seems to have some bias on it provided by a resistive potential divider between +ve and 0 volts. Presumably the device is using g2 to provide bias in enhancement mode. To be honest I have never experimented much with these devices. It was always change them if suspect, when I used to repair receivers as a job. They actually rarely gave trouble. Alan.