Datasheet

LT1800
15
1800fa
TYPICAL APPLICATIONS
Single 3V Supply, 1MHz, 4th Order Butterworth Filter
The circuit shown in Figure 4 makes use of the low voltage
operation and the wide bandwidth of the LT1800 to create
a DC accurate 1MHz 4th order lowpass fi lter powered from
a 3V supply. The amplifi ers are confi gured in the inverting
mode for the lowest distortion and the output can swing
rail-to-rail for maximum dynamic range. Figure 5 displays
the frequency response of the fi lter. Stopband attenuation
is greater than 100dB at 50MHz. With a 2.25V
P-P
, 250kHz
input signal, the fi lter has harmonic distortion products
of less than –85dBc. Worst-case output offset voltage is
less than 6mV.
Figure 4. 3V, 1MHz, 4th Order Butterworth Filter
Figure 5. Frequency Response of Filter
–
+
LT1800
909Ω
V
IN
V
S
/2
V
OUT
1800 F04
220pF
909Ω 2.67k
–
+
LT1800
1.1k
22pF
3V
470pF
2.21k
1.1k
47pF
FREQUENCY (Hz)
–80
GAIN (dB)
–40
0
–100
–60
–20
1k 100k 1M 10M 100M
1800 F05
–120
10k