AD8067 Analog Devices, AD8067 Datasheet - Page 19

• Manufacturer Part Number: AD8067
• Manufacturer: Analog Devices

Specifications of AD8067

• Vcc-vee: 5V to 24V
• Isy Per Amplifier: 7mA
• Packages: SOT
• -3db Bandwidth: 54MHz
• Slew Rate: 640V/µs
• Vos: 200µV
• Ib: 0.6pA
• # Opamps Per Pkg: 1
• Input Noise (nv/rthz): 6.6nV/rtHz

Test data for the preamp is shown in Figure 52 and Figure 53.
100
95
90
85
80
75
70
65
60
0.01
Figure 52. Photodiode Preamplifier Frequency Response
CH1
Figure 53. Photodiode Preamplifier Pulse Response
500mV
T
0.1
FREQUENCY – MHz
1
M 50ns CH1 830mV
10
C1 RISE
31.2ns
C1 FALL
31.6ns
100
Rev. A | Page 19 of 24
USING THE AD8067 AT GAINS OF LESS THAN 8
A common technique used to stabilize de-compensated
amplifiers is to increase the noise gain, independent of the
signal gain. The AD8067 can be used in applications where the
signal gain is less than 8, if proper care is taken to ensure that
the noise gain of the amplifier is set to at least the recommended
minimum signal gain of 8 (see Figure 54).
The signal and noise gain equations for a noninverting
amplifier are:
The addition of resistor R2 modifies the noise gain equation.
Note the signal gain equation has not changed.
This technique allows the designer to use the AD8067 in gain
configurations of less than 8. The drawback to this type of
compensation is that the input noise and offset voltages are
also amplified by the value of the noise gain. In addition, the
distortion performance is degraded. To avoid excessive
overshoot and ringing when driving a capacitive load, the
AD8067 should be buffered by a small series resistor; in this
case, a 51 Ω resistor was used.
Signal
Noise
Noise
V
IN
301Ω
R1
Gain
Gain
Gain
50Ω
Figure 54. Gain of Less than 2 Schematic
R2
= 1
=
= 1
1 +
+
+
R3
R1
R1
R3
R1
4
3
AD8067
R3
||
–5V
R2
+5V
600Ω
R3
5
2
0.1μF
0.1μF
10μF
1
10μF
C4
C1
C2
C3
51Ω
R4
R
AD8067
L
V
OUT