OPA687
OPA687
www.ti.com
TM
Wideband, Ultra-Low Noise,
Voltage Feedback OPERATIONAL AMPLIFIER
With Power Down
APPLICATIONS
● LOW DISTORTION ADC DRIVER
● OC-3 FIBER OPTIC RECEIVER
● LOW NOISE DIFFERENTIAL AMPLIFIERS
● EQUALIZING RECEIVERS
FEATURES
● HIGH GAIN BANDWIDTH: 3.8GHz
● LOW INPUT VOLTAGE NOISE: 0.95nV/√Hz
● VERY LOW DISTORTION: –95dBc (5MHz)
● LOW DISABLED POWER: 2mW
● VERY HIGH SLEW RATE: 900V/µs
● STABLE FOR G ≥ 12
● ULTRASOUND CHANNEL AMPLIFIERS
● IMPROVED REPLACEMENT FOR THE
CLC425
stages. As a voltage gain stage, the OPA687 is opti-
mized for a flat frequency response at a gain of +20 and
is guaranteed stable down to gains of +12. New external
compensation techniques allows the OPA687 to be used
at any inverting gain with excellent frequency response
control. Using this compensation can give an extremely
high dynamic range ADC driver to support > 40MSPS
12- and 14-bit converters.
DESCRIPTION
The OPA687 combines a very high gain bandwidth and
large signal performance with an ultra-low input noise
voltage (0.95nV/√Hz) while dissipating only 18mA sup-
ply current. Where power savings is paramount, the
OPA687 also includes an optional power down pin that,
when pulled low, will disable the amplifier and decrease
the quiescent current to only 1% of its powered up value.
This optional feature may be left disconnected to insure
normal amplifier operation when no power-down is re-
quired.
OPA687 RELATED PRODUCTS
INPUT NOISE
VOLTAGE (nV/√Hz)
GAIN BANDWIDTH
PRODUCT (MHz)
SINGLES
DUAL
The combination of low input voltage and current noise,
along with a 3.8GHz gain bandwidth product, make the
OPA687 an ideal amplifier for wideband transimpedance
OPA642
OPA643
OPA686
—
—
2.7
2.3
1.3
210
800
OPA2686
1600
+5V
+5V
VCM
20Ω
–60
OPA687
100Ω
1.7pF
–65
–70
–75
–80
–85
VIN
+
4Vp-p
–5V
50Ω Source
80pF
39pF
39pF
850Ω
1:2
ADS852
14-Bit
65MSPS
< 6dB
Noise
Figure
850Ω
2Vp-p
+5V
OPA687
–5V
VIN
–
100Ω
1.7pF
80pF
20Ω
0
5
10
15 20
25
30 35
40
45 50
VCM
Center Frequency (MHz)
Ultra-High Dynamic Range
Differential Input ADC Driver
Measured 2-Tone, 3rd-Order Distortion for
Differential ADC Driver.
Copyright © 1998, Texas Instruments Incorporated
SBOS065A
Printed in U.S.A. January, 2001