Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: driver circuit for FET
Mon Dec 27, 2004 9:43 am
Joined: Thu Nov
04, 2004 9:02 pm
I am looking for some
info on the design of a driver circuit to convert TTL input to control
voltages to the FET gate to switch it on and off.
Post subject: FET Driver Circuit
Unread postPosted: Mon Dec 27, 2004 1:56 pm
If you go onto the
Hittite website (www.hittite.com) and look at the data sheet for the
HMC232C8 you will see a suggested driver circuit. Hittite switches are
fets which are controlled by their gates.
Post subject: TTL FET driver
Sun Jan 02, 2005 4:02 pm
Joined: Sun Oct
31, 2004 3:01 pm
I use a
TTL source to drive a FET connected to VCC to power on/off cell phone
circuits. The FET source is tied to Vcc through 100K resistor to the
Gate. The TTL source pulls the gate high or low depending.
you are concerned abourt continuous power you could drop the gate input
voltage with a series diode or a voltage. I have not had to use either
and they waste battery life, although that may not matter to your application.
Unread postPosted: Mon Jan 03,
2005 4:19 am
Joined: Thu Nov 04, 2004
Can you explain further.
I cannot follow the connections to source and gaet that you have explained.
FET Driver Circuit
Unread postPosted: Mon Jan 03, 2005 9:44 am
What Gary is suggesting is to place a 100K ohm resistor between
the gate of the FET and the source. VCC of 5V mus be applied at the
source. When 0V is applied to the gate, then VGS=0-5=-5V, therefore
turning FET off. If 5V is applied to the gate, then VGS=5-5=0V and FET
will be on. This is a common technique, you just have to make sure to
use blocking caps at the outputs/inputs and if you use shunt FETS to
float them with a capacitor to ground. I would attach a schematic but
do not think this forum has that capability?
Post subject: Thanks
Unread postPosted: Wed Jan
05, 2005 1:50 pm
Joined: Thu Nov 04, 2004
Thanks for the info. I actually had to convert
0v and 5v to -2v and 0.5v; I figured how to do it now.
Post subject: Re: driver circuit for FET
Unread postPosted: Thu Jan 20, 2005 9:40 am
I am looking for some info on the design of a driver circuit
to convert TTL input to control voltages to the FET gate to switch it
on and off.