MIC7201

Micrel

MIC7201

6

December 1998

Applications Information

Input Common Mode Voltage

The MIC7201 tolerates overdriving the inputs by at least

300mV beyond either rail without producing phase inversion.

If the absolute maximum input voltage is exceeded, the input

current should be limited to

±5mA to prevent reducing reliabil-

ity. A 10k

Ω series input resistor, used as a current limiter will

protect the input structure from voltages as large as 50V

above the supply or below ground.

Output Voltage Swing

Output resistance of the MIC7201 is symmetric; sink and

source output resistances are equal. Output voltage swing is

determined by the load and, given the approximate output

resistance, which may be readily calculated with the following

formula:

R

V

I

OUT

DROP

LOAD

≈

V

stage. V

(output swing) portion of the appropriate Electrical Character-

istics table. I

minus V+/2 and divided by R

Electrical Characteristics DC (5V) table, the typical output

voltage drop using a 2k

Ω load (connected to V+/2) is 0.015V,

which produces an I

Then:

R

15mV

1.243mA

1

≈

12 1

2

.

Ω

Driving Capacitive Loads

Driving a capacitive load introduces phase-lag into the output

signal, and this in turn reduces system phase margin. The

application that is least forgiving of reduced phase margin is

a unity gain amplifier. The MIC7201 typically can drive a

500pF capacitive load connected directly to its output.

DAC

0.1µF

0.1µF

Digital

Input

0.1µF

0.1µF

4.7µF

MIC7201

Figure 1. Audio DAC

IN+

OUT

50k

100k

V+

50k

50k

100k

IN–

V–

MIC7201

1

2

3

4

5

V

V

2

OUT

IN

=

Figure 2. Gain of One-Half

IN+

OUT

50k

100k

V+

50k

50k

100k

IN–

V–

MIC7201

1

2

3

4

5

V

V+

2

Figure 3. Voltage Follower

IN+

OUT

50k

100k

V+

50k

50k

100k

IN–

V–

MIC7201

1

2

3

4

5

0.1µF

Figure 4. Inverting Unity Gain

IN+

OUT

50k

100k

V+

50k

50k

100k

IN–

V–

MIC7201

1

2

3

4

5

0.1µF

V

V

2

OUT

V+

=

Figure 5. Virtual Ground Generator