Re: switching FETs or relays

On Sep 2, 9:38 pm, "Mis...@xxxxxxxxx" <Mis...@xxxxxxxxx> wrote:
I want to run my amplifier via batteries and use a TTL driven switch
to turn it ON, only when it's needed - to save power. So for +/- 12
volts with 20 mA should i go with FETs or just used mechanical
switches?

Here you go. This uses a pair of N and P channel mosfets along with
some level shifting. It also incorporates current limiting for start
up and just in case. Sorry about the limited, lack of, explanation and
component values.

Grab hold of LTSpice.....

http://www.linear.com/designtools/software/switchercad.jsp

Then cut and paste the text below into Notepad and save the file with
an .asc extension. Then you can load it into LTspice to look at it.


Version 4
*** 1 880 920
WIRE -208 -224 -256 -224
WIRE -176 -224 -208 -224
WIRE -64 -224 -96 -224
WIRE 0 -224 -64 -224
WIRE 352 -224 96 -224
WIRE -64 -192 -64 -224
WIRE -208 -128 -208 -224
WIRE -112 -128 -208 -128
WIRE 16 -128 16 -176
WIRE 16 -128 -16 -128
WIRE -208 -48 -208 -128
WIRE -192 -48 -208 -48
WIRE 16 -48 16 -128
WIRE 16 -48 -112 -48
WIRE 16 -16 16 -48
WIRE 16 96 16 64
WIRE 112 144 80 144
WIRE 160 144 112 144
WIRE 288 144 240 144
WIRE 416 144 352 144
WIRE 112 176 112 144
WIRE 16 240 16 192
WIRE 112 288 112 256
WIRE 112 288 80 288
WIRE 352 288 352 160
WIRE 352 288 112 288
WIRE 352 320 352 288
WIRE 16 368 16 336
WIRE -192 480 -224 480
WIRE 16 480 16 448
WIRE 16 480 -112 480
WIRE -224 560 -224 480
WIRE -112 560 -224 560
WIRE 16 560 16 480
WIRE 16 560 -16 560
WIRE 16 608 16 560
WIRE -224 656 -224 560
WIRE -224 656 -256 656
WIRE -192 656 -224 656
WIRE -64 656 -64 624
WIRE -64 656 -112 656
WIRE 0 656 -64 656
WIRE 352 656 96 656
FLAG 352 320 0
FLAG 416 144 CTRL
IOPIN 416 144 In
FLAG -256 -224 +12
IOPIN -256 -224 In
FLAG -256 656 -12
IOPIN -256 656 In
FLAG 352 -224 +12S
IOPIN 352 -224 Out
FLAG 352 656 -12S
IOPIN 352 656 Out
SYMBOL pmos 96 -176 M270
WINDOW 0 98 83 VLeft 0
WINDOW 3 74 83 VLeft 0
SYMATTR InstName M1
SYMBOL nmos 96 608 R90
WINDOW 0 71 47 VRight 0
WINDOW 3 95 10 VRight 0
SYMATTR InstName M2
SYMBOL npn 80 96 M0
WINDOW 0 79 36 Left 0
WINDOW 3 61 60 Left 0
SYMATTR InstName Q1
SYMBOL pnp 80 336 R180
WINDOW 0 83 60 Left 0
WINDOW 3 70 34 Left 0
SYMATTR InstName Q2
SYMBOL Digital\\buf1 352 80 M0
SYMATTR InstName TTL
SYMBOL res -208 -32 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 0 56 VBottom 0
SYMATTR InstName R1
SYMATTR Value 10K
SYMBOL res -96 464 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 10K
SYMBOL res 96 160 R0
WINDOW 0 38 50 Left 0
SYMATTR InstName R3
SYMATTR Value 2K2
SYMBOL res 256 128 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 4K7
SYMBOL res -80 -240 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R5
SYMATTR Value 6R8
SYMBOL res -96 640 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R6
SYMATTR Value 6R8
SYMBOL pnp -16 -192 R90
WINDOW 0 83 42 VRight 0
WINDOW 3 108 26 VRight 0
SYMATTR InstName Q3
SYMBOL npn -16 624 M270
WINDOW 0 104 72 VLeft 0
WINDOW 3 79 70 VLeft 0
SYMATTR InstName Q4
SYMBOL res 0 -32 R0
WINDOW 0 36 51 Left 0
SYMATTR InstName R7
SYMATTR Value 4K7
SYMBOL res 0 352 R0
WINDOW 0 40 50 Left 0
SYMATTR InstName R8
SYMATTR Value 4K7

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