UTC571
LINEAR INTEGRATED CIRCUIT
+20
0
MAXIMUM
SIGNAL LEVEL
-20
-40
-60
-80
-100
90dB
110dB
NOISE IN
20kHz BW
-40
-20
0
VCA GAIN (0dB)
Figure 12. Dynamic Range of UTC571
Figure 12 shows the noise performance of the DG cell. The maximum output level before clipping occurs in the
gain cell is plotted along with the output noise in a 20kHz bandwidth. Note that the noise drops as the gain is
reduced for the first 20dB of gain reduction. At high gains, the signal to noise ratio is 90dB, and the total dynamic
range from maximum signal to minimum noise is 110dB.
Control signal feedthrough is generated in the gain cell by imperfect device matching and mismatches in the
current sources, I 1 and I 2 . When no input signal is present, changing I G will cause a small output signal. The
distortion trim is effective in nulling out any control signal feedthrough, but in general, the null for minimum
feedthrough will be different than the null in distortion. The control signal feedthrough can be trimmed
independently of distortion by tying a current source to the DG input pin. This effectively trims I . Figure 17 shows
such a trim network.
Vcc
R-SELECT FOR
3.6V
470k
100k
TO PIN 3 OR 14
Figure 13. control Signal Feedthrough
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YOUW ANG ELECTRONICS CO.LTD
UTC [ Unisonic Technologies ]
