THS4041 Datasheet, PDF (13/28 Pages) Texas Instruments – 165-MHz C-STABLE HIGH-SPEED AMPLIFIERS

THS4041, THS4042
165-MHz C-STABLE HIGH-SPEED AMPLIFIERS
SLOS237B– MAY 1999 – REVISED FEBRUARY 2000
APPLICATION INFORMATION
theory of operation
The THS404x 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 62.
(7) VCC +
IN – (2)
(6) OUT
IN + (3)
(4) VCC –
NULL (1)
NULL (8)
Figure 62. THS4041 Simplified Schematic
noise calculations and noise figure
Noise can cause errors on very small signals. This is especially true when amplifying small signals, where
signal-to-noise ration (SNR) is very important. The noise model for the THS404x is shown in Figure 63. 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 )
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
13