linsw01
Modifications
Date
Name
Date
Name
Description
Schematic no.
Page no.
Pages
A
B
C
D
E
F
1
2
3
4
Linear Amp Solid-State Switch
EVS2010/101 version 1.02
GM4EVS
19-Sep-10
DJ
Q2
MPSA42
R5
1k
D1
1N4007
D3
1N4007
J3
J2
Linear Amp Switch - high positive voltage
To linear
relay connector
typically +100 volts o/c
KENWOOD
From tx/rx keying line
- typically +12v on tx
TX: 12 volts RX: 0 volts
TX current: about 10mA
E
B
C
MPSA42
NPN device
Vce max = 300 volts
Ic max = 500 mA
Hfe = 40 min.
The value of R4 is selected to apply about 10mA of base current to Q2 during
transmit. This ensures that Q2, which has a low gain, is saturated and turns
on hard.
Should Q2 fail with a collector-base short, then D1 and D2 stop any high
voltage getting back into the transceiver.
For Kenwood-only switching, Q1 and its associated components can be
omitted.
Design Notes
( high positive voltage )
Original date
01-Mar-2010
1
1
Q1
2N3906
D2
1N4007
R1
100R
C1
100n
R3
4.7k
R4
1k
R2
10k
J1
+12 v
YAESU
From tx/rx keying line
- open collector o/p
TX: 0 volts RX: 11.4 volts
TX current: about 1mA
E
B
C
PNP device
Vce max = 40 volts
Ic max = 200 mA
Hfe = 100 min.
2N3906
YAESU
TX current: about 12mA
RX current: 0mA
D3 clamps relay
switching back-emf
D4
1N4007