LMH6503 Datasheet, PDF (18/20 Pages) National Semiconductor (TI) – Wideband, Low Power, Linear Variable Gain Amplifier

Application Circuits
FOUR-QUADRANT MULTIPLIER
Applications requiring multiplication, squaring or other non-
linear functions can be implemented with four-quadrant mul-
tipliers. The LMH6503 implements a four-quadrant multiplier
as illustrated in Figure 11:
2^nd ORDER TUNABLE BANDPASS FILTER
The LMH6503 Variable-Gain Amplifier placed into a feed-
back loop provides signal processing function such as in a
2nd order tunable bandpass filter. The center frequency of
the 2nd order bandpass shown in Figure 13 is adjusted
through the use of the LMH6503’s gain control voltage, V_G.
The integrators implemented with two sections of a
LMH6682, provide the coefficients for the transfer function.
20073958
FIGURE 11. Four Quadrant Multiplier
FREQUENCY SHAPING
Frequency shaping and bandwidth extension of the
LMH6503 can be accomplished using parallel networks con-
nected across the R_G ports. The network shown in the
Figure 12 schematic will effectively extend the LMH6503’s
bandwidth.
20073960
20073959
FIGURE 12. Frequency Shaping
20073961
FIGURE 13. Tunable Bandpass Filter
www.national.com
18