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Amps drive video signals close to zero volts

Geneva — STMicroelectronics Inc. introduced two single-supply, 300-MHz amplifiers that were designed to drive high-definition signals on 75-ohm video lines at close to zero volts — in high-end industrial and medical imaging systems, and in HDTV-enabled set-top boxes and DVD players.

The TSH340 and TSH341 video amplifiers feature operation on a single 3-volt to 5-V single power supply.

The TSH340 is a buffer with internal gain; the gain is set at 6 dB to allow the right level of video signal while maintaining good line matching, the company said.

The TSH341 is an op-amp that uses the same voltage feedback architecture as the TSH340, but allows the gain to be set externally. Both use a high-speed 0.25-micron complementary manufacturing technology to achieve up to 300-MHz bandwidth with quiescent current of 9.8 milliamps.

High slew rates, low distortion and a gain flatness of 65 MHz, combined with a low input-voltage noise of 7 nanovolts/√ Hz, make the TSH340 and TSH341 devices suitable to drive digital-to-analog (D/A) converter outputs on 75-ohm video lines, according to STMicroelectronics.

The amplifiers are input/output negative rail, which allows them to drive the signal to within 60 mV of ground — guaranteed by production testing — while operating on a single 5-V supply, and enables the video signal to be driven directly from the D/A converter output without any transition capacitance, the company said.

The amplifiers are specified for both 150-ohm and 100-ohm loads, and are supplied in the tiny SOT23-5 and SO8 plastic packages.

The TSH340 and TSH341 video amplifiers are supported by an evaluation board. They are available in volume now for $1.50 each in 5,000-piece quantities. Click here for the TSH340 data sheet. Click here for the TSH341 data sheet.

STMicroelectronics Inc. , 1-781-861-2650, www.st.com.

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