Technical Info Key Consideration When Selecting a Preamplifier

Technical Info Key Consideration When Selecting a Preamplifier
Technical Info
Key Consideration When Selecting a Preamplifier
The most important role of a preamplifier is to faithfully amplify the input signal. The ideal
preamplifier should be providing a sufficient wide range, generating no noise by itself, no
waveform distortion, hardly being affected by temp. change and over time change.
It’ s important to select the optimal preamplifier for the application under specific conditions.
1 Input Signal Level
In some applications, gain may be set using several stages of amplifiers due to a very low input
signal level. In such setups, it’ s particularly important to use a low-noise amplifier in the initial
stage since any noise generated there will be amplified by the following stage.
2 Gain
There are fixed gain amplifiers and switchable gain amplifiers. If the input signal level is
unknown or greatly changed, selects a switchable gain amplifier.
3 Input Mode
There are a single wire ground input and a differential input. If the gain and the frequency
characteristics are same, the amplifier with single wire ground input achieves lower noise. If the
external noise is large, you can reduce the influence of external noise by using a differential
input amplifier. "
4 Signal Frequency Range
We should consider whether we need the amplifier to accommodate DC at the lower end of the
frequency range and what the upper limit of that range will be. Amplifiers with a wide range
exhibit fast response and produce waveforms with a faithful leading edge. However, a wide
range also results in more noise, so we should choose an amplifier that matches the frequency of
the signal.
Key Consideration When Selecting a Preamplifier
Technical Info
5 Input and Output Impedance
The ideal low-frequency amplifier has sufficiently high input impedance and low output
As for high-frequency amplifier (over 10 MHz), its input and output impedance should match
with a coaxial line" (50 Ω in general)
6 For Current Output Sensor Uses
If you use the current-output sensor, select a transimpedance amplifier (Current to voltage converter) . In this case, the amplifier should have low input impedance. Since the capacitance of
the sensor affects the amplifier’s frequency characteristics, the input cable length between the
sensor and the amplifier should be minimized.
It’ s also necessary to consider factors such as the amplifier’ s maximum output voltage, input
noise, input offset, offset drift, distortion, size, power supply, and power consumption.
Low Noise Preamplifier SA-230F5
(voltage amplifier)
Frequency range: 1 kHz to 100 MHz
Input type: Single-ended
Input impedance: 50 Ω
Equivalent input noise voltage density: 0.25 nV/√ Hz
Noise figure: 0.6 dB
Gain: 46 dB
Wideband Current Amplifier SA-604F2
(current to voltage converter)
Frequency range: DC to 500 kHz
Input type: Single-ended
Input impedance: 1 kΩ
Equivalent input noise current density: 45 fA/√ Hz
Gain (V/A): 1×107 (10 M)
Low Noise DC Power Supply LP5393
Output Noise: 10 µVrms or lower (typ.) (10 Hz to 20 MHz bandwidth)
Output Voltage Stability: ±20 ppm/°C (typ.)
Output Voltage: ±12 V to ±15 V
Output Current: ±0.1 A max.
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