SSM2019BN 데이터 시트보기 (PDF) - Analog Devices
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SSM2019BN Datasheet PDF : 8 Pages
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SSM2019
V+
+IN
RG
–IN
RG1
SSM2019
OUT
RG2
REFERENCE
G=
VOUT = 10k⍀ + 1 V–
(+IN) – (–IN)
RG
Figure 1. Basic Circuit Connections
VS = ؎15V
TA = 25؇C
60
40
20
0
GAIN
The SSM2019 only requires a single external resistor to set the
voltage gain. The voltage gain, G, is:
G
=
10 kW
RG
+
1
and the external gain resistor, RG , is:
RG
=
10 kW
G –1
For convenience, Table I lists various values of RG for common
gain levels.
Table I. Values of RG for Various Gain Levels
RG (⍀) AV dB
NC
4.7 k
1.1 k
330
100
32
10
1
0
3.2 10
10 20
31.3 30
100 40
314 50
1000 60
The voltage gain can range from 1 to 3500. A gain set resistor is
not required for unity gain applications. Metal film or wire-wound
resistors are recommended for best results.
The total gain accuracy of the SSM2019 is determined by the
tolerance of the external gain set resistor, RG, combined with the
gain equation accuracy of the SSM2019. Total gain drift combines
the mismatch of the external gain set resistor drift with that of
the internal resistors (20 ppm/∞C typ).
Bandwidth of the SSM2019 is relatively independent of gain,
as shown in Figure 2. For a voltage gain of 1000, the SSM2019
has a small-signal bandwidth of 200 kHz. At unity gain, the
bandwidth of the SSM2019 exceeds 4 MHz.
1k
10k
100k
1M
10M
Figure 2. Bandwidth for Various Values of Gain
NOISE PERFORMANCE
The SSM2019 is a very low noise audio preamplifier exhibiting
a typical voltage noise density of only 1 nV/÷Hz at 1 kHz. The
exceptionally low noise characteristics of the SSM2019 are in
part achieved by operating the input transistors at high collector
currents since the voltage noise is inversely proportional to the
square root of the collector current. Current noise, however, is
directly proportional to the square root of the collector current.
As a result, the outstanding voltage noise performance of the
SSM2019 is obtained at the expense of current noise performance.
At low preamplifier gains, the effect of the SSM2019 voltage
and current noise is insignificant.
The total noise of an audio preamplifier channel can be calculated by:
En = en 2 + (in RS )2 + et 2
where:
En = total input referred noise
en = amplifier voltage noise
in = amplifier current noise
RS = source resistance
et = source resistance thermal noise
For a microphone preamplifier, using a typical microphone
impedance of 150 W, the total input referred noise is:
En = (1 nV Hz )2 + 2( pA / Hz ¥ 150 W)2 + (1.6 nV / Hz )2 =
1.93 nV / Hz @ 1 kHz
where:
en = 1 nV/÷Hz @ 1 kHz, SSM2019 en
in = 2 pA/÷Hz @ 1 kHz, SSM2019 in
RS = 150 W, microphone source impedance
et = 1.6 nV/÷Hz @ 1 kHz, microphone thermal noise
This total noise is extremely low and makes the SSM2019
virtually transparent to the user.
–6–
REV. 0
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