THS4011 Datasheet, PDF (14/30 Pages) Texas Instruments – 290-MHz LOW-DISTORTION HIGH-SPEED AMPLIFIERS

THS4011, THS4012
290-MHz LOW-DISTORTION HIGH-SPEED AMPLIFIERS
SLOS216B – JUNE 1999 – FEBRUARY 2000
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
f_Ts 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.
(7) VCC +
IN – (2)
(6) OUT
IN + (3)
(4) VCC –
NULL (1)
NULL (8)
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 (e_Rx = 4 kTR_x )
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