Ricoh R5RL User Manual
Page 20
R
×
5RL
17
• CURRENT BOOST CIRCUIT
Output current of 60mA or more can be obtained by
the current boost circuit constructed as shown in this cir-
cuit diagram.
• CURRENT BOOST CIRCUIT WITH OVERCURRENT LIMIT CIRCUIT
A circuit for protecting Tr.1 from the destruction
caused by output short-circuit or overcurrent is shown in
this circuit diagram.
When the voltage reduction caused by the current ( aa
I
OUT
) which flows through R2 reaches Vbe2 of Tr.2 by
additionally providing the current boost circuit with Tr.2
and R2, Tr.2 is turned ON and the base current of Tr.1 is
increased, so that the output current is limited.
Current limit of Overcurrent Limit Circuit is obtained
as follows :
I
OUT
Vbe2/R2
• CURRENT SOURCE
A current source with the structure as shown in this
circuit diagram can be used. Output Current I
OUT
is
obtained as follows :
I
OUT
= Vreg /R + I
SS
Take care that Output Current I
OUT
does not exceed
its allowable current.
C2
GND
GND
GND
R
×
5RL
SERIES
V
OUT
V
OUT
C1
V
IN
V
IN
Tr.1
+
+
C2
GND
GND
GND
R
×
5RL
SERIES
V
OUT
V
OUT
C1
V
IN
V
IN
Tr.1
Tr.2
R1
R2
I
OUT
Vbe2
+
+
GND
R
×
5RL
SERIES
C1
V
IN
V
IN
R
I
OUT
I
SS
V
OUT
+
*
1) Vreg : Set Output Voltage of R
×
5RL Series.
*
1