LMV791MK/NOPB National Semiconductor, LMV791MK/NOPB Datasheet - Page 16

• Manufacturer Part Number: LMV791MK/NOPB
• Description: IC OP AMP CMOS 1.8V TSOT23-6
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LMV791MK/NOPB

• Amplifier Type: General Purpose
• Number Of Circuits: 1
• Output Type: Rail-to-Rail
• Slew Rate: 11.5 V/µs
• Gain Bandwidth Product: 17MHz
• Current - Input Bias: 0.1pA
• Voltage - Input Offset: 100µV
• Current - Supply: 1.15mA
• Current - Output / Channel: 60mA
• Voltage - Supply, Single/dual (±): 1.8 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-6, TSOT-6
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Other names: LMV791MK; LMV791MKNOPB; LMV791MKNOPBTR; LMV791MKNOPBTR; LMV791MKTR

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AUDIO PREAMPLIFIER WITH BANDPASS FILTERING
With low input referred voltage noise, low supply voltage and
low supply current, and a low harmonic distortion, the
LMV791 family is ideal for audio applications. Its wide unity
gain bandwidth allows it to provide large gain for a wide range
of frequencies and it can be used to design a preamplifier to
drive a load of as low as 600Ω with less than 0.01% distortion.
Two amplifier circuits are shown in Figure 5 and Figure 6.
Figure 5 is an inverting amplifier, with a 10 kΩ feedback re-
sistor, R
gain of −10. Figure 6 is a non-inverting amplifier, using the
same values of R
of these circuits, the coupling capacitor C
frequency at which the circuit starts providing gain, while the
feedback capacitor C
gain starts dropping off. Figure 7 shows the frequency re-
sponse of the inverting amplifier with different values of C
FIGURE 6. Non-inverting Audio Preamplifier
2
, and a 1kΩ input resistor, R
FIGURE 5. Inverting Audio Preamplifier
1
and R
F
decides the frequency at which the
2
, and provides a gain of 11. In either
1
, and hence provides a
C1
decides the lower
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F
.
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TRANSIMPEDANCE AMPLIFIER
CMOS input op amps are often used in transimpedance ap-
plications as they have an extremely high input impedance.
A transimpedance amplifier converts a small input current into
a voltage. This current is usually generated by a photodiode.
The transimpedance gain, measured as the ratio of the output
voltage to the input current, is expected to be large and wide-
band. Since the circuit deals with currents in the range of a
few nA, low noise performance is essential. The LMV791/
LMV792 are CMOS input op amps providing wide bandwidth
and low noise performance, and are hence ideal for tran-
simpedance applications.
Usually, a transimpedance amplifier is designed on the basis
of the current source driving the input. A photodiode is a very
common capacitive current source, which requires tran-
simpedance gain for transforming its miniscule current into
easily detectable voltages. The photodiode and amplifier’s
gain are selected with respect to the speed and accuracy re-
quired of the circuit. A faster circuit would require a photodi-
ode with lesser capacitance and a faster amplifier. A more
sensitive circuit would require a sensitive photodiode and a
high gain. A typical transimpedance amplifier is shown in Fig-
ure 8. The output voltage of the amplifier is given by the
equation V
is limited, R
of I
The LMV791/LMV792 have a large gain-bandwidth product
(17 MHz), which enables high gains at wide bandwidths. A
rail-to-rail output swing at 5.5V supply allows detection and
amplification of a wide range of input currents. A CMOS input
stage with negligible input current noise and low input voltage
noise allows the LMV791/LMV792 to provide high fidelity am-
plification for wide bandwidths. These properties make the
LMV791/LMV792 ideal for systems requiring wide-band tran-
simpedance amplification.
FIGURE 7. Frequency Response of the Inverting Audio
IN
can be detected.
OUT
F
should be selected such that all possible values
= −I
IN
R
F
. Since the output swing of the amplifier
Preamplifier
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