Datasheet

ICL7652
Advanced LinCMOSTM PRECISION CHOPPER-STABILIZED
OPERATIONAL AMPLIFIER
TYPICAL APPLICA TION DA T A
The low-frequency noise of a chopper amplifier depends on the magnitude of the component noise prior to
chopping and the capability of the circuit to reduce this noise while chopping. The use of the Advanced
linCMOSTM process, with its low-noise analog MOS transistors and patent-pending input stage design,
significantly reduces the input noise voltage.
The primary source of nonideal operation in chopper-stabilized amplifiers is error charge from the switches.
As charge imbalance accumulates on critical nodes, input offset voltage can increase, especially with
increasing chopping frequency. This problem has been significantly reduced in the ICl7652 by use of a
patent-pending compensation circuit and the Advanced linCMOSTM process.
The ICl7652 incorporates a feed-forward design that ensures continuous frequency response. Essentially,
the gain magnitude of the nulling amplifier and compensation network crosses unity at the break frequency
of the main amplifier. As a result, the high-frequency response of the system is the same as the frequency
response of the main amplifier. This approach also ensures that the slewing characteristics remain the same
during both the nulling and amplifying phases.
temperature coefficient of input offset voltage
Figure 27 shows the effects of package-induced thermal EMF. The ICL7652 can null only the offset voltage
within its nulling loop. There are metal-to-metal junctions outside the nulling loop (bonding wires, solder joints,
etc.) that produce EMF. In Figure 27, an ICL7652 was placed in an oven at 25°C at t = 0, biased up, and
allowed to stabilize. At t = 3 min, the oven was turned on and allowed to rise in temperature to 125°C. As
evidenced by the curve, the overall change in input offset voltage with temperature is much less than the
specified maximum limit of 0.05 !lV/OC.
VIO = VO/1000
0.1 ~F
-1t-
50kQ
-'\/v'v-
~ 5Y 10 t
1+ -5Y YO
0.1 ~F 50 kQ
+
FIGURE 27. EFFECTS OF PACKAGE-INDUCED THERMAL EMF
TEXAS ~
INSTRUMENTS
POST OFFICE BOX 655303 .DALLAS, TEXAS 75265
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