RC4157M Fairchild Semiconductor, RC4157M Datasheet - Page 8

• Manufacturer Part Number: RC4157M
• Description: Op Amps
• Manufacturer: Fairchild Semiconductor

Specifications of RC4157M

• Number Of Channels: 4
• Voltage Gain Db: 100 dB
• Common Mode Rejection Ratio (min): 80 dB
• Input Offset Voltage: 5 mV
• Supply Current: 7 mA
• Maximum Power Dissipation: 300 mW
• Maximum Operating Temperature: + 70 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-14 Wide
• Maximum Dual Supply Voltage: +/- 20 V
• Minimum Operating Temperature: 0 C
• Lead Free Status / Rohs Status: No

PRODUCT SPECIFICATION
characteristics. The values shown for C1, C2, R4, R5 and R6
are arbitrary. Pre-selecting their values will simplify the filter
tuning procedures, but other values can be used if necessary.
The generalized transfer function for the state-variable active
filter is:
Filter response is conventionally described in terms of a nat-
ural frequency
complex pole pair. The filter parameters
the coefficients in T(s) as:
8
T s
0
=
=
b
a
----------------------------------- -
s
0
2
2
s
2
and
+
+
b
a
1
1
s
Q
s
0
V1
V
+
* Input connections are chosen for inverting or non-inverting response. Values of
** Values of R1 and R2 determine natural frequency.
+
N
in radians/sec, and Q, the quality of the
=
b
R3,R7,R8 determine gain and Q.
---------------------------------- - V
R4
a
0
0
----- -
b
0
-------------------- -
R3
0
+
R3R5
R3*
R8*
-------------------- -
R3
+
R3R5
R7*
R5
+
R5
3
2
HP
4156/57
100K
R6
s
A
Figure 15. 2-Pole State-Variable Active Filter
10K
100K
R4
+
R5
0
---------------------------------- - V
R5
and Q relate to
-------------------- -
R3
Highpass
+
R3R4
1
Ouput
-------------------- -
R3
V
+
R3R4
HP
R4
+
R1**
R4
Equation 1.
LP
6
5
s
4156/57
+
1000 pF
---------------------------------- - V
R3
The input configuration determines the polarity (inverting or
non-inverting), and the output selection determines the type
of filter response (lowpass, bandpass, or highpass).
Notch and all-pass configurations can be implemented by
adding another summing amplifier.
Bandpass filters are of particular importance in audio and
telecommunication equipment. A design approach to band-
pass filters will be shown as an example of the state-variable
configuration.
Design Example Bandpass Filter
For the bandpass active filter (Figure 16) the input signal is
applied through R3 to the inverting input of the summing
amplifier and the output is taken from the first integrator
(V
the inverting and non-inverting inputs (see Equation 1).
B
C1
-------------------- -
R4
BP
+
R4R5
-------------------- -
R4
). The summing amplifier will maintain equal voltage at
+
R4R5
R5
Bandpass
7
+
Output
R5
V
BP
IN
R2**
s
+
10
-------------------- - V
R6
9
R7
4156/57
+
R7
1000 pF
C
C2
BP
65-0751
s
Lowpass
8
Output
V
LP
REV. 1.0.1 6/13/01
RC4156/RC4157