The circuits on this page are presented as a collection of circuit idea's. They do NOT include full construction details ,component values, etc. Most of these circuits have been built by myself, and others . Please excuse any errors.

SIMPLE VARIABLE VOLTAGE REGULATED POWER SUPPLY

Using BUZ71 mosfet.

I use this circuit in my bench supply. The tab (Drain) of the mosfet can be grounded directly to the metal case. This eliminates the need for the usual mica insulating kit. The very low on resistance, and high input resistance of the mosfet, results in very good voltage regulation. Important note, the 0v (-) input is at a lower potential than ground, and must not be grounded. This circuit looks a bit more conventional if you turn it upside down Hi!. You will need the usual Transformer, rectifier, capacitor arrangement (not shown) to get the unregulated, input voltage.

HIGH CURRENT SUPPLY

High current (20A) PSU with over voltage protection and over current 'trip' protection. I use this supply for my 100 Watt SSB/CW rig.

HIGH LEVEL RX PASSIVE MIXER

USING SWITCHING MOSFETS

This mixer was grafted into the front of my home brew HF rig in place of the original dual bridge diode mixer. It compared well with the diode mixer, even on 40M at night. High power mosfets worked well on 160M and 80M, but were no good on the higher bands. Medium power (about 1 Watt) high speed switching fets gave very good results on all HF bands. The IRFD113 worked well, the IRFD1Z3 also gave good results. Dead, or obsolete hard drives are a good source of surface mount medium power switching mosfet's. Note that this is a passive mixer, no power supply to the fet's. You will need several volts p/p of local oscillator drive. Ideally this type of mixer should have a symmetrical square wave loc. osc. but it works well with a sine wave.

A CRUDE BUT EFFECTIVE CROWBAR CIRCUIT

This circuit will protect your 12V equipment from overvoltage in the event of a PSU regulator failure. Use a high current stud mounting SCR or TRIAC. I used a 40 Amp triac. Remember that this device works by short circuiting the output of your PSU. Make sure that you have the correct fuse fitted. The crowbar circuit will react very quickly if the supply voltage goes over 17.5Vdc (even for a few microseconds). you may need to slow it down by putting a capacitor across the 100R resistor.Try about 0.1 mfd.