Low Noise, High Speed Amplifier
for 16-Bit Systems
AD8021
Rev. F
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FEATURES
Low noise
2.1 nV/√Hz input voltage noise
2.1 pA/√Hz input current noise
Custom compensation
Constant bandwidth from G = −1 to G = −10
High speed
200 MHz (G = −1)
190 MHz (G = −10)
Low power
34 mW or 6.7 mA typical for 5 V supply
Output disable feature, 1.3 mA
Low distortion
−93 dBc second harmonic, f
C
= 1 MHz
−108 dBc third harmonic, f
C
= 1 MHz
DC precision
1 mV maximum input offset voltage
0.5 μV/°C input offset voltage drift
Wide supply range, 5 V to 24 V
Low price
Small packaging
Available in SOIC-8 and MSOP-8
APPLICATIONS
ADC preamps and drivers
Instrumentation preamps
Active filters
Portable instrumentation
Line receivers
Precision instruments
Ultrasound signal processing
High gain circuits
GENERAL DESCRIPTION
The AD8021 is an exceptionally high performance, high speed
voltage feedback amplifier that can be used in 16-bit resolution
systems. It is designed to have both low voltage and low current
noise (2.1 nV/√Hz typical and 2.1 pA/√Hz typical) while operating
at the lowest quiescent supply current (7 mA @ ±5 V) among
today’s high speed, low noise op amps. The AD8021 operates
over a wide range of supply voltages from ±2.25 V to ±12 V, as
well as from single 5 V supplies, making it ideal for high speed,
low power instruments. An output disable pin allows further
reduction of the quiescent supply current to 1.3 mA.
CONNECTION DIAGRAM
8
7
6
5
1
2
3
4
LOGIC
REFERENCE
–IN
+IN
–V
S
DISABLE
+V
S
V
OUT
C
COMP
AD8021
01888-001
Figure 1. SOIC-8 (R-8) and MSOP-8 (RM-8)
The AD8021 allows the user to choose the gain bandwidth
product that best suits the application. With a single capacitor,
the user can compensate the AD8021 for the desired gain with
little trade-off in bandwidth. The AD8021 is a well-behaved
amplifier that settles to 0.01% in 23 ns for a 1 V step. It has a fast
overload recovery of 50 ns.
The AD8021 is stable over temperature with low input offset
voltage drift and input bias current drift, 0.5 μV/°C and 10 nA/°C,
respectively. The AD8021 is also capable of driving a 75 Ω line
with ±3 V video signals.
The AD8021 is both technically superior and priced considerably
less than comparable amps drawing much higher quiescent
current. The AD8021 is a high speed, general-purpose amplifier,
ideal for a wide variety of gain configurations and can be used
throughout a signal processing chain and in control loops. The
AD8021 is available in both standard 8-lead SOIC and MSOP
packages in the industrial temperature range of −40°C to +85°C.
FREQUENCY (Hz)
0.1M 1G1M 10M 100M
CLOSED-LOOP GAIN (dB)
24
21
–6
18
15
12
9
6
3
0
–3
V
OUT
= 50mV p-p
G = –10, R
F
= 1kΩ, R
G
= 100Ω,
R
IN
= 100Ω, C
C
= 0pF
G = –5, R
F
= 1kΩ, R
G
= 200Ω,
R
IN
= 66.5Ω, C
C
= 1.5pF
G = –2, R
F
= 499Ω, R
G
= 249Ω,
R
IN
= 63.4Ω, C
C
= 4pF
G = –1, R
F
= 499Ω, R
G
= 499Ω,
R
IN
= 56.2Ω, C
C
= 7pF
01888-002
Figure 2. Small Signal Frequency Response
