LM148J/883 National Semiconductor, LM148J/883 Datasheet - Page 7

• Manufacturer Part Number: LM148J/883
• Description: IC,Operational Amplifier,QUAD,BIPOLAR,DIP,14PIN,CERAMIC
• Manufacturer: National Semiconductor

Application Hints
As with most amplifiers, care should be taken lead dress,
component placement and supply decoupling in order to
ensure stability. For example, resistors from the output to an
input should be placed with the body close to the input to
minimize “pickup” and maximize the frequency of the
feedback pole which capacitance from the input to ground
creates.
A feedback pole is created when the feedback around any
amplifier is resistive. The parallel resistance and capacitance
Typical Applications—LM148
f
R1 = 100k pot. C1 = 0.0047 µF, C2 = 0.01 µF, C3 = 0.1 µF, R2 = R6 = R7 = 1M,
R3 = 5.1k, R4 = 12 , R5 = 240 , Q = NS5102, D1 = 1N914, D2 = 3.6V avalanche
diode (ex. LM103), V
A simpler version with some distortion degradation at high frequencies can be made by using A1 as a simple inverting amplifier, and by putting back to back
zeners in the feedback loop of A3.
MAX
= 5 kHz, THD
S
0.03%
=
±
15V
(Continued)
One Decade Low Distortion Sinewave Generator
7
from the input of the device (usually the inverting input) to AC
ground set the frequency of the pole. In many instances the
frequency of this pole is much greater than the expected 3
dB frequency of the closed loop gain and consequently there
is negligible effect on stability margin. However, if the
feedback pole is less than approximately six times the
expected 3 dB frequency a lead capacitor should be placed
from the output to the input of the op amp. The value of the
added capacitor should be such that the RC time constant of
this capacitor and the resistance it parallels is greater than or
equal to the original feedback pole time constant.
DS007786-8
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