Small Signal Preamplification — Choosing Bandwidth, Gain, and Input Impedance

Detecting a very small electrical signal reliably means amplifying it without adding noise that swamps the signal itself. Aigtek's ATA-5000 series optical preamplifier is built specifically for this role, with up to 60dB gain and noise performance suited to genuinely weak signal detection rather than general-purpose amplification.

Why Preamplification Is a Distinct Discipline From Power Amplification

A power amplifier's job is delivering current and voltage to a load; a preamplifier's job is raising a weak signal's level while adding as little additional noise as possible, so the signal remains usable for subsequent measurement or processing. These are different design priorities, which is why the ATA-5000 series is a dedicated product line rather than simply a lower-power variant of Aigtek's power amplifiers.

The Model Range — Frequency and Gain Combinations

Ten of the eleven models follow a consistent pattern: five bandwidth tiers from 5MHz to 100MHz, each available at either 46dB or 60dB gain, all with 50Ω input impedance for standard coaxial signal sources. The ATA-5120 is the exception — a DC-coupled, high-input-impedance (10kΩ) variant for sources that shouldn't be loaded with a 50Ω termination, at the cost of bandwidth extending only to 1kHz.

Selecting Bandwidth and Gain Together

Choose the bandwidth tier that comfortably covers your signal's frequency content, then select 46dB or 60dB gain based on how weak the input signal actually is — 60dB gain amplifies noise on the input by the same factor as the signal, so it's not simply a "more gain is always better" choice. For sources that need to see a high input impedance rather than a 50Ω termination, the ATA-5120 is the only model in the range built for that condition, and its restricted bandwidth should be checked against your application before selection.

Finch Electronic Solutions — Melbourne, Australia
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