KH231
DATA SHEET
Offset Voltage Adjustment
If trimming of the input offset voltage (V
os
= V
ni
-V
in
) is
desired, a resistor value of 10kΩ to 1MΩ placed between
pins 8 and 9 will cause V
os
to become more negative by
8mV to 0.2mV respectively. Similarly, a resistor placed
between pins 1 and 2 will cause V
os
, to become more
positive.
Thermal Considerations
At high ambient temperatures or large internal power
dissipations, heat sinking is required to maintain
acceptable junction temperatures. Use the thermal
model on the previous page to determine junction
temperatures. Many styles of heat sinks are available for
TO-8 packages; the Thermalloy 2240 and 2268 are good
examples. Some heat sinks are the radial fin type which
cover the pc board and may interfere with external
components. An excellent solution to this problem is to
use surface mounted resistors and capacitors. They
have a very low profile and actually improve high
frequency performance. For use of these heat sinks with
conventional components, a 0.1” high spacer can be inserted
under the TO-8 package to allow sufficient clearance.
T
case
100°C/W
T
j(pnp)
P
pnp
100°C/W
T
j(npn)
P
npn
17.5
°
C/W
T
j(circuit)
P
circuit
+
-
T
ambient
θ
ca
θ
ca
= 65°C/W for the KH231 without heat sink in still air.
30°C/W for the KH231 with a Wakefield 215 heat
sink in still air.
10°C/W for the KH231 with a Wakefield 215 heat
sink at 300 ft/min air.
30°C/W for the KH231 with a Thermalloy 2240A
heat sink in still air.
5°C/W for the KH231 with a Thermalloy 2240A
heat sink at 500 ft/min air.
For example, with the KH231 operating at ±15V while
driving a 100Ω load at 15V
pp
output (50% duty cycle
pulse waveform, DC = 0), P
(npn)
= P
(pnp)
= 190mW (R
col
= 33) and P
(cir)
= 0.48W. Then with the Wakefield
215 heat sink and air flow of 300 ft/min the output
transistors’ T
j
is 28°C above ambient and worst case T
j
in
the rest of the circuit is 32°C above ambient. In still air,
however, the rise in T
j
is 45°C and 49°C, respectively.
With no heat sink, the rise in T
j
is 75°C and 79°C,
respectively! Under most conditions,
HEAT SINKING IS
REQUIRED.
Other methods of heat sinking may be used, but for
best results, make contact with the base of the KH231
package, use a large thermal capacity heat sink and use
forced air convection.
Low V
CC
Operation: Supply Current Adjustment
The KH231 is designed to operate on supplies as low as
±5V. In order to improve full bandwidth at reduced sup-
ply voltages, the supply current (I
CC
) must be increased.
The plot of Bandwidth vs. V
CC
, shows the effect of short-
ing pins 1 and 2 and pins 8 and 9; this will increase both
bandwidth and supply current. Care should be taken to
not exceed the maximum junction temperatures; for this
reason this technique should not be used with supplies
exceeding ±10V. For intermediate values of V
CC
,
external resistors between pins 1 and 2 and pins 8 and 9
can be used.
P
(circuit)
= (I
CC
)((+V
CC
) – (V
CC
)) where I
CC
= 16mA at ±15V
P
(xxx)
= [(±V
CC
) – V
out
– (I
col
) (R
col
+ 4)] (I
col
) (%Duty)
For positive V
o
and V
CC
, this is the power in the npn
device. For negative V
o
and V
CC
, this is the power in the
pnp device.
I
col
= V
o
/R
L
or 4mA, whichever is greater. (Include feed-
back R in R
L
.)
R
col
is a resistor (33Ω recommended) between the xxx
collector and ±V
CC
.
The limiting factor for output current and voltage is junction
temperature. Of secondary importance is I
(out)
, which
should not exceed 150mA.
T
j(pnp)
= P
(pnp)
(100 +
θ
ca
) + (P
(cir)
+ P
(npn)
)(θ
ca
) + T
a
,
similar for T
j(npn)
.
T
j(cir)
= P
(cir)
(48 +
θ
ca
) + (P
(pnp)
+ P
(npn)
)(θ
ca
) + T
a
.
REV. 1A January 2004
5
CADEKA [ CADEKA MICROCIRCUITS LLC. ]
