LM13700N National Semiconductor, LM13700N Datasheet - Page 10

• Manufacturer Part Number: LM13700N
• Description: Operational Amplifier (Op-Amp) IC
• Manufacturer: National Semiconductor

Specifications of LM13700N

• No. Of Amplifiers: 2
• Slew Rate: 50V/µs
• No. Of Pins: 16
• Peak Reflow Compatible (260 C): No
• Input Bias Current: 1µA
• Supply Voltage: 36V
• Output Current: 20mA
• Input Offset Voltage Max: 4mV
• Gain: 2dB
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Voltage Controlled Resistors
Voltage Controlled Filters
OTA’s are extremely useful for implementing voltage con-
trolled filters, with the LM13700 having the advantage that
the required buffers are included on the I.C. The VC Lo-Pass
Filter of Figure 11 performs as a unity-gain buffer amplifier at
frequencies below cut-off, with the cut-off frequency being
the point at which X
R
RC roll-off (6 dB per octave) of the input signal amplitude
with a −3 dB point defined by the given equation, where g
A
). At frequencies above cut-off the circuit provides a single
C
/g
m
equals the closed-loop gain of (R/
FIGURE 9. Voltage Controlled Resistor with Linearizing Diodes
FIGURE 8. Voltage Controlled Resistor, Single-Ended
(Continued)
m
10
is again 19.2 x I
VC High-Pass Filter which operates in much the same man-
ner, providing a single RC roll-off below the defined cut-off
frequency.
Additional amplifiers may be used to implement higher order
filters as demonstrated by the two-pole Butterworth Lo-Pass
Filter of Figure 13 and the state variable filter of Figure 14 .
Due to the excellent g
filters perform well over several decades of frequency.
ABC
at room temperature. Figure 12 shows a
m
tracking of the two amplifiers, these
DS007981-15
DS007981-16