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3. Choosing a Preamplifier

Onda’s preamplifiers are designed as an electronic and
mechanical match with the hydrophones. The AH and AG series
preamplifiers add a 20 dB gain. There are a few items to
consider when choosing a preamplifier.

3.1 Frequency Response
The AH-1100 preamplifiers have a bandwidth of 25 MHz. The
AH-20x0 submersible preamplifiers are available with either a
25 MHz or 100 MHz bandwidth (denoted by -25 and -100 after
the model number). For high frequency applications, a higher
bandwidth preamplifier is recommended. However, this has the
trade-off of increase in electrical noise.
The bandwidth of the AG-20x0 preamplifiers is 60 MHz. Their
downward sloped frequency response compensates for the
characteristic high frequency sensitivity of the HGL hydrophones
to provide a flatter combined response. Therefore, the AG series
preamplifiers are generally recommended for HGL’s while the
AH preamplifiers are recommended for other hydrophone types.

Gain [dB]  25                                      PreamApGlif-i2er01(N0oise Level)
           20                                             AH-(2260010µ-V1r0m0s)
           15                                             AH-201((0316-60002µµ5VVrrmmss))
           10                                             AH-1100

            5      20 40 60 80 100
            0                Frequency [MHz]

                0                                                                         29

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