11

LT1492/LT1493

Supply Voltage

The LT1492/LT1493 op amps are fully functional and all

internal bias circuits are in regulation with 2.1V of supply.

The amplifiers will continue to function with as little as

1.6V, although the input common mode range and the

phase margin are about gone. The minimum operating

supply voltage is guaranteed by the PSRR tests that are

done with the input common mode equal to 500mV and a

minimum supply voltage of 2.5V.

The positive supply pin of the LT1492/LT1493 should be

bypassed with a small capacitor (about 0.01

µF) within an

inch of the pin. When driving heavy loads and for good

settling time, an additional 4.7

µF capacitor should be

used. When using split supplies, the same is true for the

negative supply pin.

Power Dissipation

The LT1492/LT1493 combine high speed and large output

drive in small packages. Because of the wide supply

voltage range, it is possible to exceed the maximum

junction temperature under certain conditions. Maximum

Worst-case power dissipation occurs at the maximum

supply current and when the output voltage is at 1/2 of

either supply voltage (or the maximum swing if less than

Example: LT1493 at 70

Inputs

Typically, at room temperature, the inputs of the LT1492/

and to within 1.2V of the positive supply with the amplifier

still functional. However, the input bias current will shift as

shown in the characteristic curves. For full precision

performance, the common mode range should be limited

more than about 700mV, that input current will increase

dramatically. The current is limited by internal 100

Ω

resistors between the input pins and diodes to each

supply. The output will remain low (no phase reversal) for

to sink current, such as in a single supply system with a 1k

load to ground, there is no phase reversal for inputs up to

8V below ground.

There are no clamps across the inputs of the LT1492/

LT1493 and therefore each input can be forced to any

voltage between the supplies. The input current will re-

main constant at about 50nA over most of this range.

When an input gets closer than 1.5V to the positive supply,

that input current will gradually decrease to zero until the

input goes above the supply, then will increase due to the

previously mentioned diodes. If the inverting input is held

more positive than the noninverting input by 200mV or

more, while at the same time the noninverting input is

increase by 1mA and the noninverting input current will

increase to about 10

µA. This should be kept in mind in

comparator applications where the inverting input stays

Output

The output of the LT1492/LT1493 will swing to within

0.65V of the positive supply and to within 3mV of the

negative supply with no load. Under loaded conditions see

the Typical Performance curves for the output saturation

voltage characteristics.

The output of the LT1492/LT1493 has reverse-biased

diodes to each supply. If the output is forced beyond either

supply, unlimited currents will flow. If the current is

transient and limited to several hundred milliamps, no

damage will occur.