LT1011 Datasheet, PDF (9/16 Pages) Linear Technology – Voltage Comparator

LT1011/LT1011A
APPLICATIONS INFORMATION
In the “off” state, I₁ is switched off and both Q1 and Q2 turn
off. The collector of Q2 can be now held at any voltage
above V ^– without conducting current, including voltages
above the positive supply level. Maximum voltage above
V ^– is 50V for the LT1011M and 40V for the LT1011C/I. The
emitter can be held at any voltage between V ⁺ and V ^– as
long as it is negative with respect to the collector.
In the “on” state, I₁ is connected, turning on Q1 and Q2.
Diodes D1 and D2 prevent deep saturation of Q2 to
improve speed and also limit the drive current of Q1. The
R1/R2 divider sets the saturation voltage of Q2 and pro-
vides turn-off drive. Either the collector or emitter pin can
be held at a voltage between V ⁺ and V ^–. This allows the
remaining pin to drive the load. In typical applications, the
emitter is connected to V ^– or ground and the collector
drives a load tied to V ⁺ or a separate positive supply.
When the emitter is used as the output, the collector is
typically tied to V⁺ and the load is connected to ground or
V^–. Note that the emitter output is phase reversed with
respect to the collector output so that the “+” and “–” input
designations must be reversed. When the collector is tied
to V⁺, the voltage at the emitter in the “on” state is about
2V below V⁺ (see curves).
Input Signal Range
The common mode input voltage range of the LT1011 is
about 300mV above the negative supply and 1.5V below
the positive supply, independent of the actual supply
voltages (see curve in the Typical Performance Character-
istics). This is the voltage range over which the output will
respond correctly when the common mode voltage is
applied to one input and a higher or lower signal is applied
to the remaining input. If one input is inside the common
mode range and one is outside, the output will be correct.
If the inputs are outside the common mode range in
opposite directions, the output will still be correct. If both
inputs are outside the common mode range in the same
direction, the output will not respond to the differential
input; for temperatures of 25°C and above, the output will
remain unconditionally high (collector output), for tem-
peratures below 25°C, the output becomes undefined.
TYPICAL APPLICATIONS
Offset Balancing
R2
3k
R1
20k
V⁺
5
2₊
6
8
LT1011
7
3_–
1011 TA03
Driving Load Referenced
to Positive Supply
V⁺
V ⁺⁺
3_–
8
7
LT1011
2₊
1
4
R_LOAD
VV
OR
GROUND
V ⁺⁺ CAN BE GREATER OR LESS THAN V ⁺
1011 TA05
Driving Load Referenced
to Negative Supply
V⁺
V
2_–
8
INPUTS* LT1011
3₊
4
7
1
R_LOAD
V
1011 TA06
*INPUT POLARITY IS REVERSED
WHEN USING PIN 1 AS OUTPUT
9