QA605 Datasheet, PDF (1/2 Pages) List of Unclassifed Manufacturers – Low Noise Preamplifier

QA 605
Low Noise Preamplifier
Rev. 1.1
Shortform Datasheet
Features:
• Low Noise Preamplifier
• For 200Ω…5kΩ Source
Impedance Range
• Low 1/f Corner Frequency
• Low Quiescent Current
• High Speed
• No External Components
Required
• Hermetically Sealed Metal
Package (DIL-14)
Applications:
Sonar, Instrumentation, Sensor
Frontend
Production to MIL-Standards
(MIL-PRF-38534 / MIL-STD 883C/D/E )
available on request.
Circuit Description:
Low noise monolithic circuits generally have quite high current noise densities, rendering
them unsuitable for source impedances (real value) of over 250Ω, not to mention
impedances of 1kΩ or higher. Bias current of the input differential pair in a low noise amplifier
has to be relatively high to reduce input noise voltage density. In the case of a bipolar input
stage, this would cause the input bias current to rise beyond acceptable levels. Therefore
designers often provided the input stage with current sources - which make the input current
noise density even worse and may cause instabilities for higher source impedances.
This hybrid design shows none of the above mentioned drawbacks: Current noise density is
low even with excellent voltage noise density, the amplifier has low input bias current and will
not become unstable for high source impedances.
The circuit topology is internally differential, but with single ended input and output. There are
generally no external components required to run the amplifier, supply bypass capacitors are
integrated. However, if you intend to run the amplifier with high output load, additional bypass
capacitors (tantalum) are recommended. The amplifier fits into DIL-14 sockets and features a
hermetically closed (welded) metal package which provides RFI-protection and high reliability
even under difficult environmental conditons.
The amplifier is recommended for ultrasonic signal conditioning, especially for transducer
impedances in the 1kΩ range and frequencies up to 1.5MHz. By its outstanding DC input
characteristics the amplifier also qualifies for low noise instrumentation or sensor
applications.
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