LM359

SNOSBT4C – MAY 1999 – REVISED MARCH 2013

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APPLICATION HINTS

The LM359 consists of two wide bandwidth, decompensated current differencing (Norton) amplifiers. Although

similar in operation to the original LM3900, design emphasis for these amplifiers has been placed on obtaining

much higher frequency performance as illustrated in Figure 23.

This significant improvement in frequency response is the result of using a common-emitter/common-base

(cascode) gain stage which is typical in many discrete and integrated video and RF circuit designs. Another

versatile aspect of these amplifiers is the ability to externally program many internal amplifier parameters to suit

the requirements of a wide variety of applications in which this type of amplifier can be used.

Figure 23.

DC BIASING

The LM359 is intended for single supply voltage operation which requires DC biasing of the output. The current

mirror circuitry which provides the non-inverting input for the amplifier also facilitates DC biasing the output. The

basic operation of this current mirror is that the current (both DC and AC) flowing into the non-inverting input will

of how closely these two currents match. For more details see TI Application Note AN-72 (Literature Number

SNOA666).

requiring the output to provide the (

−) input current. This forces the output DC level to be whatever value

necessary (within the output voltage swing of the amplifier) to provide this DC reference current, Figure 24.

Figure 24.

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