50W

50W

200W

V

OUT+

V

OUT-

200W

V

IN-

V

IN+

Differential

Output

Differential

Input

THS770012

THS770012

SLOS669C

– FEBRUARY 2010 – REVISED JANUARY 2012

www.ti.com

THEORY OF OPERATION

GENERAL DESCRIPTION

The THS770012 is a wideband, fully differential amplifier designed and optimized specifically for driving 14-bit

and 16-bit ADCs at input frequencies up to 200MHz. This device provides high bandwidth, low distortion, and low

noise, which are critical parameters in high-speed data acquisition systems that require very high dynamic range,

such as wireless base stations and test and measurement applications. It also makes an excellent differential

amplifier for general-purpose, high-speed differential signal chain and short line-driver applications. The device

has an operating power-supply range of 4.75V to 5.5V. The THS770012 has proprietary circuitry to provide very

fast recovery from overdrive conditions and has a power-down mode for power saving. The THS770012 is

offered in a Pb-free (RoHS compliant) and green, QFN-24 thermally-enhanced package. It is characterized for

operation over the industrial temperature range of

–40°C to +85°C.

The amplifier uses two negative-feedback loops. One is for the primary differential amplifier and the other

controls the common-mode operation.

Primary Differential Amplifier

The primary amplifier of the THS770012 is a fully-differential op amp with on-chip gain setting resistors. The gain

of the device can be changed by using external components as described in Setting the Gain section below. The

The output common-mode voltage is controlled through a second negative-feedback loop. The output

gain and bandwidth of the loop). For more details on fully-differential amplifier theory and use, see application

report SLOA054, Fully-Differential Amplifiers, available for download from www.ti.com.

OPERATION

Differential to Differential

The THS770012 is a fully-differential amplifier that can be used to amplify differential input signals to differential

output signals. A basic block diagram of the circuit with nominal gain of +12dB is shown in Figure 38. The

differential input to differential output configuration gives the best performance; the signal source and load should

be balanced.

Figure 38. Differential Input to Differential Output Amplifier

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Product Folder Link(s): THS770012