2 µs/DIV

CONTROL

OUTPUT

0V

LMH6732

SNOSA47B – FEBRUARY 2003 – REVISED MARCH 2013

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DIFFERENTIAL GAIN AND PHASE

Differential gain and phase are measurements useful primarily in composite video channels. They are measured

by monitoring the gain and phase changes of a high frequency carrier (3.58MHz for NTSC and 4.43MHz for PAL

systems) as the output of the amplifier is swept over a range of DC voltages. Specifications for the LMH6732

the following:

DC sweep range: 0 to 100 IRE units (black to white)

Carrier: 4.43MHz at 40 IRE units peak to peak

SOURCE IMPEDANCE

For best results, source impedance in the non-inverting circuit configuration (see Figure 59) should be kept below

5k

Ω.

Above 5k

Ω it is possible for oscillation to occur, depending on other circuit board parasitics. For high signal

source impedances, a resistor with a value of less than 5k

Ω may be used to terminate the non-inverting input to

ground.

FEEDBACK RESISTOR

In current-feedback op amps, the value of the feedback resistor plays a major role in determining amplifier

dynamics. It is important to select the correct value. The LMH6732 provides optimum performance with feedback

resistors as shown in Table 2 below. Selection of an incorrect value can lead to severe roll-off in frequency

response, (if the resistor value is too large) or , peaking or oscillation (if the value is too low).

Gain (V/V)

Unit

9

3.4

1

700

1k

1k

Ω

700

1k

1k

Ω

500

750

1k

Ω

400

450

1k

Ω

500

500

1k

Ω

200

200

1k

Ω

1k

1k

1k

Ω

500

500

1k

Ω

20

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