Quad Micropower Op Amp
Features
Quad micro power op amp
·
Wide range of supply voltage: 1.6V~5.5V
·
High input impedance
·
Single supply operation
·
Low current consumption: < 5mA per amp
·
Rail to rail output
·
Provides both sink and source output drive
·
capability
Applications
Battery powered system
·
Sensor amplifier
·
Low power gain blocks
·
Low power comparators
·
General Description
The HT9274 is a CMOS quad micro-power op
erational amplifier featuring high input imped
ance, extremely low power, high gain and high
stability.
It allows common mode input voltage range
which extends below the negative rail, output
swings to both rails with a reasonable sink and
souce capability of the output drive current.
This cost-effective device is suitable for high
HT9274
Common mode input extends below nega
·
tive rail
Pin compatible with LM324/WT274 (14-pin
·
DIP)
14-pin DIP/SOP package
·
Signal detectors
·
Active filters
·
Caller ID systems
·
Communication systems
·
gain, low frequency, low power applications, es
pecially ideal for battery powered systems
where mA range of standby current is essential
for long battery life span. For example, in
multi-standard Caller ID systems, HT9274 is
ideal as a low power line signal monitor/detector, and in car alarm systems, the HT9274 is excellent for piezo vibratile detector signal
amplifier application.
-
-
Comparison Table
ITEM
HT9274 1.6~5.5V
WT274 1.35~10V
LM324 3~32V
Operating
Voltage
Operating
Current
5mA 500mA 500mA
9mA16mA
400mA
Output
Source
Current
20mA 8mA 45nA 1MHz
Output
Sink
Current
2mA 1pA 0.1MHz
1 November 23, 1999
Input Bias
Current
1pA 0.1MHz
GBW
Max. load
(To VDD
or VSS)
>10kW
>500kW
>2kW
Block Diagram
HT9274
Pin Assignment
1O U T
1IN
1IN +
VDD
2IN +
2IN
2O U T
4O U T
-
-
1O U T
1IN
1IN +
VDD
2IN +
2IN
2O U T
1
-
2
3
4
5
-
6
7
14
4O U T
13
4IN
-
12
4IN +
11
VSS
10
3IN +
9
3IN
-
8
3O U T
4IN
4IN +
VSS
3IN +
3IN
3O U T
-
-
H T9274
1 4 D IP /S O P
2 November 23, 1999
Pin Description
HT9274
Pin No. Pin Name I/O
1 1OUT O CMOS OUT Output pin of the op amp 1
2
3 1IN+ I PMOS IN Noninverting input pin of the op amp 1
4 VDD
5 2IN+ I PMOS IN Noninverting input pin of the op amp 2
6
7 2OUT O CMOS OUT Output pin of the op amp 2
8 3OUT O CMOS OUT Output pin of the op amp 3
9
10 3IN+ I PMOS IN Noninverting input pin of the op amp 3
11 VSS
12 4IN+ I PMOS IN Noninverting input pin of the op amp 4
13
14 4OUT O CMOS OUT Output pin of the op amp 4
1IN-
¾¾
2IN-
3IN-
¾¾
4IN-
Internal
Connection
I PMOS IN Inverting input pin of the op amp 1
Positive power supply
I PMOS IN Inverting input pin of the op amp 2
I PMOS IN Inverting input pin of the op amp 3
Negative power supply
I PMOS IN Inverting input pin of the op amp 4
Description
Absolute Maximum Ratings
Supply Voltage.................................-0.3V to 6V
Input Voltage .................V
Note: These are stress ratings only. Stresses exceeding the range specified under "Absolute Maxi-
mum Ratings" may cause substantial damage to the device. Functional operation of this device
at other conditions beyond those listed in the specification is not implied and prolonged exposure to extreme conditions may affect device reliability.
-0.3V to VDD+0.3V
SS
Storage Temperature.................-50°Cto125°C
Operating Temperature ..............-20°Cto75°C
3 November 23, 1999
Pin Description
HT9274
Pin No. Pin Name I/O
1 1OUT O CMOS OUT Output pin of the op amp 1
2
3 1IN+ I PMOS IN Noninverting input pin of the op amp 1
4 VDD
5 2IN+ I PMOS IN Noninverting input pin of the op amp 2
6
7 2OUT O CMOS OUT Output pin of the op amp 2
8 3OUT O CMOS OUT Output pin of the op amp 3
9
10 3IN+ I PMOS IN Noninverting input pin of the op amp 3
11 VSS
12 4IN+ I PMOS IN Noninverting input pin of the op amp 4
13
14 4OUT O CMOS OUT Output pin of the op amp 4
1IN-
¾¾
2IN-
3IN-
¾¾
4IN-
Internal
Connection
I PMOS IN Inverting input pin of the op amp 1
Positive power supply
I PMOS IN Inverting input pin of the op amp 2
I PMOS IN Inverting input pin of the op amp 3
Negative power supply
I PMOS IN Inverting input pin of the op amp 4
Description
4 November 23, 1999
Functional Description
HT9274
Input stage
The input stage of op amps are nominal PMOS
differential amplifiers (see the following dia
gram), therefore the common mode input volt
age can extend to V
-0.6V. On the other hand
SS
the common mode input voltage has to be main
tained below (V
-1)V to keep the input device
DD
(M2 and M3) active. This implies that when us
ing HT9274 as a voltage follower, the input as
well as output active range will be limited be
tween V
SS~VDD
any voltage greater than V
V
-0.6V to the input pins, otherwise the inter
SS
-1V (approx.). Avoid applying
+0.6V or less than
DD
nal input protection devices may be damaged.
V
DD
V
BIAS
M1
N oninverting In
In v e rtin g In
M2 M3
PM OS PM OS
To O utput Stage
SS
M4 M5
V
V
SS
Since the input impedance of PMOS is inherently very high, it can directly couple to high
impedance elements without loading effect. For
example, coupling to ceramic transducers, inte
grating capacitor and resistor networks.
Actually the extremly high input impedance is
its major advantage over the bipolar counter
part, in some application fields such as integra
tors where the input current of op amp can
cause significant error, the HT9274 is a better
choice than the popular LM324.
Output stage
The HT9274 uses push-pull CMOS configura
tion as the output stage of op amps to minimize
low power consumption and to provide ade
quate output driving current.
Note that the output is an unbuffered struc
ture, therefore the open loop gain will be af
fected by the load resistor since the voltage gain
of this stage can be expressed as (gm5+
gm6)´R
.
L
V
DD
-
V
BIAS
M5
OUT
From
D iffe re n tia l
Am p
M6
V
SS
Because of the consideration for minimized
power consumption, the max. output current is
limited to about 400mA for both source and sink
drive. This is believed to be enough for most low
power systems, however it is recommended to
use the load resistor of >10kW for normal applications. In case of heavy load driving, an external buffer stage using bipolar transistors is
recommended.
The HT9274 is internally compensated for AC
stability and capable to withstand up to a
100pF capacitive load.
-
-
-
-
-
-
5 November 23, 1999
Application Circuits
Micro power sensor amplifier & detector
HT9274
V
DD
SENSO R
3
2
Micro power line signal monitor
TIP
RING
V
BIAS
Micro power line voltage monitor
9
10
4
5
1
2
3
6
7
11
V
DD
1
4
5
6
11
13
12
7
8
DET_O UT
14
DET_OUT
LIN E
BATT
4
3
2
1
11
DET_O UT
6 November 23, 1999
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