THS4012CD datasheet(14/30 Pages) TI

14 / 30 page

THS4011, THS4012

290-MHz LOW-DISTORTION HIGH-SPEED AMPLIFIERS

SLOS216B – JUNE 1999 – FEBRUARY 2000

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

APPLICATION INFORMATION

theory of operation

The THS401x is a high-speed, operational amplifier configured in a voltage feedback architecture. It is built

using a 30-V, dielectrically isolated, complementary bipolar process with NPN and PNP transistors possessing

fTs of several GHz. This results in an exceptionally high performance amplifier that has a wide bandwidth, high

slew rate, fast settling time, and low distortion. A simplified schematic is shown in Figure 24.

IN – (2)

IN + (3)

NULL (1)

NULL (8)

(6) OUT

(4) VCC –

(7) VCC +

Figure 24. THS4011 Simplified Schematic

noise calculations and noise figure

Noise can cause errors on very small signals. This is especially true when amplifying small signals. The noise

model for the THS401x is shown in Figure 25. This model includes all of the noise sources as follows:

• e

n = Amplifier internal voltage noise (nV/√Hz)

• IN+ = Noninverting current noise (pA/√Hz)

• IN– = Inverting current noise (pA/√Hz)

• e

Rx = Thermal voltage noise associated with each resistor (eRx = 4 kTRx )

THS4012CD Datasheet(PDF) 14 Page - Texas Instruments