THS7001 Datasheet, PDF (3/32 Pages) Texas Instruments – 70-MHz PROGRAMMABLE-GAIN AMPLIFIERS

block diagram
PREAMP VCC+
PREAMP A IN–
PREAMP A IN+
SHDN–A
SHDN–B
PREAMP B IN+
PREAMP B IN–
PREAMP VCC–
THS7001, THS7002
70-MHz PROGRAMMABLE-GAIN AMPLIFIERS
SLOS214B – OCTOBER 1998 – REVISED AUGUST 1999
PREAMP
PGA–A
OUT A PGA–A REF IN–
G0A G1A G2A
PGA–A
GND
_
_
Preamp
+
+
CLAMP+ (VH)
PGA–A OUT
+
+
Preamp
_
_
PGA–B OUT
CLAMP– (VL)
PREAMP PGA–B REF PGA–B G0B G1B G2B
OUT B
IN–
Figure 2. THS7002 Dual Channel PGA
PGA PGA PGA–B
VCC+ VCC– GND
input preamp
To achieve the minimum input equivalent noise required for very small input signals, the input preamp is
configured as a classic voltage feedback amplifier with a minimum gain of 2 or –1. The output of the preamp
is accessible, allowing for adjustment of gain using external resistors and for external filtering between the
preamp and the PGA.
programmable gain amplifier (PGA)
The PGA is an inverting, programmable gain amplifier. The gain is digitally programmable using three control
bits (TTL-compatible terminals) that are encoded to provide eight distinct levels of gain/attenuation. Nominal
gain/attenuation is shown in Table 1.
Table 1. Nominal Gain/Attenuation
G2 G1 G0
000
001
010
011
100
101
110
111
PGA GAIN
(dB)
–22
–16
–10
–4
2
8
14
20
PGA GAIN
(V/V)
0.08
0.16
0.32
0.63
1.26
2.52
5.01
10.0
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