RC4157M Fairchild Semiconductor, RC4157M Datasheet - Page 10

• 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
These equations suggest a tuning sequence where
trimmed via R1 or R2, then Q is trimmed by varying R7
and/or R3. An important advantage of the state-variable
bandpass filter is that Q can be varied without affecting
center frequency
This analysis has assumed ideal op amps operating within
their linear range, which is a valid design approach for a
reasonable range of
values of Q, the op amp parameters become significant. A
rigorous analysis is very complex, but some factors are par-
ticularly important in designing active filters.
1. The passive component values should be chosen such
Schematic Diagram
10
(3,5,10,12)
(2,6,9,13)
that all op amps are operating within their linear region
for the anticipated range of input signals. Slew rate, out-
put current rating, and common-mode input range must
be considered. For the integrators, the current through
the feedback capacitor (I = C dV/dt) should be included
in the output current computations.
+ Input
- Input
65-0735
Q8
0
Q4
.
0
and Q. At extremes of
18K
R3
Q2
Q7
4900
R1
Q5
(1/4 shown)
Q9
Q10
Q3
22K
R4
0
and at high
C1
D2
is first
R9
30
30K
R5
Q13
Q11
2. From the equation for Q, it should seem that infinite Q
3.
The RC4156 quad operational amplifier has much better fre-
quency response than a conventional 741 circuit and is ideal
for active filter use. Natural frequencies of up to 10 kHz are
readily achieved and up to 20 kHz is practical for some con-
figurations. Q can range up to 50 with very good accuracy
and up to 500 with reasonable response. The extra gain of the
RC4156 at high frequencies gives the quad op amp an extra
margin of performance in active-filter circuits.
Q12
Q17
could be obtained by making R7 zero. But as R7 is made
small, the Q becomes limited by the op amp gain at the
frequency of interest. The effective closed-loop gain is
being increased directly as R7 is made smaller, and the
ratio of open-loop gain to closed-loop gain is becoming
less. The gain and phase error of the filter at high Q is
very dependent on the op amp open-loop gain at w
The attenuation at extremes of frequency is limited by
the op amp gain and unity-gain bandwidth. For integra-
tors, the finite open-loop op amp gain limits the accu-
racy at the low-end. The open-loop roll-off of gain limits
the filter attenuation at high frequency.
Q16
Q15
Q14
R6
20
R7
20
150
R8
Q1
Q6
Amplifier
10K
R2
Next
To
REV. 1.0.1 6/13/01
D1
F1
RC4156/RC4157
(1,7,8,14)
Outputs
(4)
+V s
(11)
-V s
0
.