Datasheet

OUTPUT
+
-
½ LME49722
10 k:
+
-
½ LME49722
11 k:
11 k:
11 k:
100 k:
100 k:
500 k:
3.6 k:
3.6 k:
1.8 k: 1.8 k:
0.05 PF
0.005 PF
0.022 PF
0.005 PF
10 PF
INPUT
+
-
OUTPUT
C1
4.7 PF
R3
150 k:
½ LME49722
R6
10 k:
R7
100:
x Total voltage noise density: e
N_total
2
| e
N
2
+ e
N_R1
2
+ e
N_R2
2
= 1.9
2
+ 2 (2.7
2
),
then e
N_total
= 4.3 nV/—Hz. For e
N_R1
= e
N_R2
| 2.7 nV/—Hz,if R1 = R2 | 470:
x Or total voltage noise = 0.13 PV input referred in a 1 kHz noise bandwidth.
LOW IMPEDANCE
MICROPHONE
R1
470:
R2
470:
R4
150 k:
LME49722
www.ti.com SNAS454A –MARCH 2008–REVISED APRIL 2013
APPLICATION INFORMATION
APPLICATION HINTS
The LME49722 is a high speed operational amplifier which can operate stably in most of the applications. For the
application with gain greater than 2, capacitive loads up to 100pF will cause little change in the phase
characteristics of the amplifiers and are therefore allowable. Capacitive loads greater than 10pF must be isolated
from the output, if the gain value is less than 2. The most straightforward way to do this is to put a resistor (its
value ≥ 20Ω ) in series with the output. The resistor will also prevent unnecessary power dissipation if the output
is accidentally shorted.
Figure 30. Low Impedance Microphone Pre-amplifier
Figure 31. Three-Band Active Tone Control
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