Datasheet

LM6132
www.ti.com SNOS751D –APRIL 2000–REVISED FEBRUARY 2013
LM6132/34 APPLICATION INFORMATION
The LM6132 brings a new level of ease of use to op amp system design.
With greater than rail-to-rail input voltage range concern over exceeding the common-mode voltage range is
eliminated.
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 high power
consumption, previously reduced battery life to unacceptable levels.
To take advantage of these features, some ideas should be kept in mind.
ENHANCED SLEW RATE
Unlike most bipolar op amps, the unique phase reversal prevention/speed-up circuit in the input stage eliminates
phase reversal and allows the slew rate to be very much a function of the input signal amplitude.
Figure 32 shows how excess input signal is routed around the input collector-base junctions directly to the
current mirrors.
The LM6132/34 input stage converts the input voltage change to a current change. This current change drives
the current mirrors through the collectors of Q1–Q2, Q3–Q4 when the input levels are normal.
If the input signal exceeds the slew rate of the input stage and the differential input voltage rises above a diode
drop, the excess signal bypasses the normal input transistors, (Q1–Q4), and is routed in correct phase through
the two additional transistors, (Q5, Q6), directly into the current mirrors.
This rerouting of excess signal allows the slew-rate to increase by a factor of 10 to 1 or more. (See Figure 31).
As the overdrive increases, the op amp reacts better than a conventional op amp. Large fast pulses will raise the
slew- rate to around 25V to 30 V/μs.
Slew Rate vs. Differential V
IN
V
S
= ±12V
Figure 31.
This effect is most noticeable at higher supply voltages and lower gains where incoming signals are likely to be
large.
This speed-up action adds stability to the system when driving large capacitive loads.
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