LM13700MX National Semiconductor, LM13700MX Datasheet - Page 11

• Manufacturer Part Number: LM13700MX
• Description: IC,Operational Amplifier,DUAL,BIPOLAR,SOP,16PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM13700MX

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Stereo Volume Control
Noting that the gain of the LM13700 amplifier of Figure 3
may be controlled by varying the linearizing diode current I
as well as by varying I
using this approach. As V
(3V
ing diodes, the increase in I
as to hold V
Voltage Controlled Resistors
An Operational Transconductance Amplifier (OTA) may be
used to implement a Voltage Controlled Resistor as shown in
Figure 8. A signal voltage applied at R
the LM13700 which is then multiplied by the g
amplifier to produce an output current, thus:
BE
) to turn on the Darlington transistors and the lineariz-
O
at that level.
ABC
O
, Figure 7 shows an AGC Amplifier
reaches a high enough amplitude
D
reduces the amplifier gain so
X
generates a V
(Continued)
FIGURE 6. Four-Quadrant Multiplier
FIGURE 7. AGC Amplifier
m
of the
IN
to
D
11
where g
by R and R
range of the LM13700 input.
Figure 9 shows a similar VCR where the linearizing diodes
are added, essentially improving the noise performance of
the resistor. A floating VCR is shown in Figure 10, where
each “end” of the “resistor” may be at any voltage within the
output voltage range of the LM13700.
m
≈ 19.2I
A
is necessary to maintain V
ABC
at 25˚C. Note that the attenuation of V
00798113
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IN
within the linear
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O