MIC6211 Datasheet, PDF (6/8 Pages) Micrel Semiconductor – IttyBitty™ Operational Amplifier Preliminary Information

MIC6211
Applications Information
Common-Mode Range and Output Voltage
The input common-mode range of the MIC6211 is from the
negative supply voltage to 1.2V below the positive supply
voltage. The output voltage swings within 1V of the positive
and negative supply voltage.
Voltage Buffer
Figure 1 shows a standard voltage follower/buffer. The output
voltage equals the input voltage. This circuit is used to buffer
a high impedance signal source. This circuit works equally
well with single or split supplies.
V_IN
3
4
1
V_OUT
V_OUT = V_IN
Figure 1. Voltage Buffer
Inverting Amplifier
Figure 2 shows an inverting amplifier with its gain set by the
ratio of two resistors. This circuit works best with split sup-
plies, but will perform with single supply systems if the non-
inverting input (+ input) is biased up above ground.
R1
R2
V_IN
4
1
V_OUT
3
V_OUT
R1
V_{IN R2}
Figure 2. Inverting Amplifer
Voltage Controlled Current Sink
Figure 3 is a voltage controlled current sink. A buffer transis-
tor forces current through a programming resistor until the
feedback loop is satisfied. Current flow is V_IN/R. This circuit
works with single or split supplies.
V_IN
3
1
4
Micrel
High-Pass Filter
Figure 4 is an active filter with 20dB (10×) gain and a low-
frequency cutoff of 10Hz. The high gain-bandwidth of the
MIC6211 allows operation beyond 100kHz. This filter con-
figuration is designed for split supplies.
0.1µF
1µF 1µF
V_IN
7.5k
332k
4
1
3
V_OUT
Figure 4a. High-Pass Filter
30
20
10
0
-10
-20
1 10 1k 100k
FREQUENCY (Hz)
Figure 4b. High-Pass Filter Response
Summing Amplifier
Figure 5 is a single supply summing amplifier. In this configu-
ration, the output voltage is the sum of V1 and V2, minus the
sum of V3 and V4. By adding more resistors to either the
inverting or non-inverting input, more voltages may be
summed. This single supply version has one important re-
striction: the sum of V1 and V2 must exceed the sum of V3
and V4, since the output voltage cannot pull below zero with
only a single supply.
R
V1
R
V2
3
R
4
1
V_OUT
R
R
V3
R
V4
All resistors are equal.
V_OUT = V1 + V2 – V3 – V4
V1 + V2 > V3 + V4 for single supply operation
Figure 5. Summing Amplifier
I
V_IN
R
R
Figure 3. Voltage Controlled Current Sink
MIC6211
6
June 1999