17/26 10.2.4 PGA VGA A Programmable Gain Instrumentation Amplifier (PGiA,PGA)is a special form of in-amp that has DGND WR A1 fixed gain levels. 26 LOGIC The appropriate gain level is selected by digital means,either by dedicated program pins,or by software interfaces(SPI or 12C). The PGiAs are perfect for those applications where gain accuracy must be maximized,or where a single PGiA can take the place of +IN 10 AD8253 several in-amps of different gain settings. +Vs 9 +Vs AD8253 AD8253 REF 1 R fHIGH-PASS =2TTRC AD8253 10M2 REF -Vs THERMOCOUPLE -Vs TRANSFORMER Vs 10.2.4 PGA VGA 1826 ◆hat are VGAs? -Variable gain amplifiers (VGAs)are signal-conditioning amplifiers with electronically settable voltage gain. There are analog VGAs and digital VGAs,or DVGAs. A digital-to-analog converter(DAC),a functional source,or a dc source can provide the analog voltage control. Ultrasound scanners and phased-array radars favor analog VGAs.They both involve a massive number of parallel amplifiers that all require a common gain control. A cable TV system in which the level of the upstream signal from the consumer's set-top box is adjusted for cable attenuation by a downstream signal from the cable company's head-end.This would be a case for a digital VGA. PRAO VGAI VGAs are available from dc to gigahertz frequencies ATTENUATOR PrA -60dB TO 0dB 1 VOUT and in a variety of 1/O INPN(5 AD8336 configurations. Relative low CMRR BIAS GAIN CONTROL compared to PGiA INTERFACE .10 13 3 11 12 NEG VPOS VCOM GPOS GNEG10.2.4 PGA / VGA ‹ A Programmable Gain Instrumentation Amplifier (PGiA, PGA) is a special form of in-amp that has fixed gain levels. ‹ The appropriate gain level is selected by digital means, either by dedicated program pins, or by software interfaces (SPI or I2C). ‹ The PGiAs are perfect for those applications where gain accuracy must be maximized, or where a single PGiA can take the place of several in-amps of different gain settings. 17/26 ‹ What are VGAs? − Variable gain amplifiers (VGAs) are signal-conditioning amplifiers with electronically settable voltage gain. − There are analog VGAs and digital VGAs, or DVGAs. − A digital-to-analog converter (DAC), a functional source, or a dc source can provide the analog voltage control. − Ultrasound scanners and phased-array radars favor analog VGAs. They both involve a massive number of parallel amplifiers that all require a common gain control. − A cable TV system in which the level of the upstream signal from the consumer’s set-top box is adjusted for cable attenuation by a downstream signal from the cable company’s head-end. This would be a case for a digital VGA. 10.2.4 PGA / VGA − VGAs are available from dc to gigahertz frequencies and in a variety of I/O configurations. − Relative low CMRR compared to PGiA 18/26