MIC7122 Datasheet, PDF (7/8 Pages) Micrel Semiconductor – Rail-to-Rail Dual Op Amp Preliminary Information

MIC7122
capacitance C_IN. The value of C_FB is determined by first
estimating C_IN and then applying the following formula:
R_IN × C_IN ≤ R_FB × C_FB
C_FB
R_FB
R_IN
V_IN
C_IN
V_OUT
Figure 2. Cancelling Feedback Phase Lag
Since a significant percentage of C_IN may be caused by board
layout, it is important to note that the correct value of C_FB may
change when changing from a breadboard to the final circuit
layout.
Typical Circuits
Some single-supply, rail-to-rail applications for which the
MIC7122 is well suited are shown in the circuit diagrams of
Figures 3 through 7.
V+
V_IN
0V to ^{V +}
A_V
1_{⁄2 MIC7122}
V_OUT
0V to V+
R2
R1 ^910k
100k
Figure 3a. Noninverting Amplifier
1V0+0
A_V
= 1+
R2
R1
≈
10
0
0
V_IN (V)
100
Figure 3b. Noninverting Amplifier Behavior
V_IN
0V to V+
V+
1_{⁄2 MIC7122}
V_OUT
0V to V+
Micrel
V_OUT = V_IN
Figure 4. Voltage Follower/Buffer
V_S
0.5V to Q1 V_CEO(sus)
V_OUT
V+
0V to V+
V_IN
0V to 2V
1_{⁄2 MIC7122}
I_OUT
{ ^Q1
2N3904
V_CEO = 40V
I_C(max) = 200mA
R_S
Change Q1 and R_S
for higher current
10Ω
1_⁄2W
and/or different gain.
I_OUT
=
V_IN
R_S
= 100mA/V
as
shown
Figure 5. Voltage-Controlled Current Sink
C1
0.001µF
R4
100k
V+
1_{⁄2 MIC7122}
V_OUT
V+
0V
R2
V+
100k
R4
R3 ^100k
100k
Figure 6. Square Wave Oscillator
C_{IN R1}
33k
R2
330k
V+
1_{⁄2 MIC7122}
C_{OUT VOUT}
0V
R_L
R3
V+
330k
C1
1µF
R4
330k
A_V
=
− ^R2
R1
=
330k
33k
=
−10
Figure 7. AC-Coupled Inverting Amplifier
March 1999
7
MIC7122