OPERATING AT LOWER SUPPLY VOLTAGES

The LMH6503 is rated for operation down to 5V supplies (V

+

-V

CMRR, PSRR, Gain vs. V

tion, at lower supplies:

a) V

V

0.5V (V

same time, gain cut-off (V

- 1V with V

Table 1 shows the approximate expressions for various

V

Table 1: V

−

V

G

Definition

Expression (V)

V

G_MIN

Gain Cut-off

0.2 x V

−

V

G_MID

A

0

V

G_MAX

A

VMAX

−0.2 x V

−

b) V

duced. This is due to limitations within the device arising

from transistor headroom. Beyond this limit, device per-

formance will be affected (non-destructive). Referring to

Figure 9, note that with V

G_LIMIT

is approaching V

duced by 1dB. This means that operating under these

conditions has reduced the maximum permissible voltage

on V

supply voltages are asymmetrical, reference Figure 9 and

Figure 10 plots to make sure the region of operation is not

overly restricted by the "pinching" of V

_MAX

curves.

c) "Max_gain" reduces. There is an intrinsic reduction in

max gain when the total supply voltage is reduced (see

Typical Performance Characteristics plots for Gain vs. V

G

(V

S

mechanism described in "b" above and shown in Figure

9.

Similar plots for V

comparison and reference.

20073936

FIGURE 8. Transformer Coupled Single Supply VGA

20073926

FIGURE 9. V

-

(V

20073925

FIGURE 10. V

-

(V

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