Typical Performance

Application Information

The LM6152/6154 is ideally suited for operation with about

10k

Ω (Feedback Resistor, R

negative input terminal.

With R

close loop gain of 10 or less, an additional small compensa-

tion capacitor (C

in order to achieve a reasonable overshoot (10%) at the out-

put by compensating for stray capacitance across the inputs.

The optimum value for C

mentally with a trimmer cap in place since its value is depen-

dant on the supply voltage, output driving load, and the oper-

ating gain. Below, some typical values used in an inverting

configuration and driving a 10k

Ω load have been tabulated

for reference:

TABLE 1. Typical BW (−3 dB) at Various

Supply Voltage and Gains

V

S

Volts

Gain

C

F

pF

BW (−3 dB)

MHz

3

−1

5.6

4

−10

6.8

1.97

−100

None

0.797

24

−1

2.2

6.6

−10

4.7

2.2

−100

None

0.962

In the non-inverting configuration, the LM6152/6154 can be

used for closed loop gains of +2 and above. In this case,

also, the compensation capacitor (C

is recommended

across R

Because of the unique structure of this amplifier, when used

at low closed loop gains, the realizable BW will be much less

than the GBW product would suggest.

The LM6152/6154 brings a new level of ease of use to op

amp system design.

The greater than rail-to-rail input voltage range eliminates

concern over exceeding the common-mode voltage range.

The rail-to-rail output swing provides the maximum possible

dynamic range at the output. This is particularly important

when operating on low supply voltages.

The high gain-bandwidth with low supply current opens new

battery powered applications where higher power consump-

tion previously reduced battery life to unacceptable levels.

The ability to drive large capacitive loads without oscillating

functional removes this common problem.

To take advantage of these features, some ideas should be

kept in mind.

The LM6152/6154, capacitive loads do not lead to oscilla-

tions, in all but the most extreme conditions, but they will re-

sult in reduced bandwidth. They also cause increased set-

tling time.

Unlike most bipolar op amps, the unique phase reversal

prevention/speed-up circuit in the input stage, caused the

slew rate to be very much a function of the input pulse ampli-

tude. This results in a 10 to 1 increase in slew rate when the

differential input signal increases. Large fast pulses will raise

the slew-rate to more than 30V/µs.

The speed-up action adds stability to the system when driv-

ing large capacitive loads.

A conventional op amp exhibits a fixed maximum slew-rate

even though the differential input voltage rises due to the

lagging output voltage. In the LM6152/6154, increasing lag

causes the differential input voltage to increase but as it

does, the increased slew-rate keeps the output following the

input much better. This effectively reduces phase lag. As a

result, the LM6152/6154 can drive capacitive loads as large

as 470 pF at gain of 2 and above, and not oscillate.

Capacitive loads decrease the phase margin of all op amps.

This can lead to overshoot, ringing and oscillation. This is

caused by the output resistance of the amplifier and the load

capacitance forming an R-C phase shift network. The

LM6152/6154 senses this phase shift and partly compen-

sates for this effect.

Total Harmonic Distortion

vs. Frequency

DS012350-31

DS012350-30

FIGURE 1. Typical Inverting Gain Circuit A

DS012350-21

FIGURE 2. Slew Rate vs. V

diff

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