THS7001 Datasheet, PDF (15/32 Pages) Texas Instruments – 70-MHz PROGRAMMABLE-GAIN AMPLIFIERS

THS7001, THS7002
70-MHz PROGRAMMABLE-GAIN AMPLIFIERS
SLOS214B – OCTOBER 1998 – REVISED AUGUST 1999
APPLICATION INFORMATION
theory of operation
Each section of the THS7001 and THS7002 consists of a pair of high speed operational amplifiers configured
in a voltage feedback architecture. They are built using a 30-V, dielectrically isolated, complementary bipolar
process with NPN and PNP transistors possessing f_Ts of several GHz. This results in exceptionally high
performance amplifiers that have a wide bandwidth, high slew rate, fast settling time, and low distortion. A
simplified schematic of the preamplifiers are shown in Figure 51.
VCC +
OUT
IN –
IN +
Figure 51. Pre-Amp Simplified Schematic
VCC –
noise calculations and noise figure
Noise can cause errors on very small signals. This is especially true for the preamplifiers, which typically amplify
small signals. The noise model is shown in Figure 52. 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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