Datasheet
0.1 PF
1 PF
0.1 PF
1 PF
820 pF
1.02 k:
62 pF
1.02 k:
V
+
-
+
V
-
510:
OUTPUT
0.1 PF
1 PF
0.1 PF
1 PF
330 pF
1.05 k:
150 pF
V
+
-
+
523:
V
-
INPUT
1.05 k:
LMH6619
LMH6619
+
-
V
IN
R
1
R
G
R
F
V
OUT
LMH6618
R
2
V
+
V
+
LMH6618, LMH6619
SNOSAV7E –AUGUST 2007–REVISED OCTOBER 2012
www.ti.com
4. V
OUTMID
= 2V + (4V – 2V)/2 = 3V
5. Gain = (4V – 2V)/(1V – 0V) = 2
6. ΔV
OUT
= 3V – 2 x 0.5V = 2
7. For the example the supply voltage will be +5V.
8. Noise gain = 2 + 2/5V = 2.4
9. R
F
= 2 kΩ
10. R
1
= 2 kΩ/2 = 1 kΩ
11. R
2
= 2 kΩ/(2.4-2) = 5 kΩ
12. R
G
= 2 kΩ/(2.4 – 1) = 1.43 kΩ
Figure 68. DC Level Shifting
4
th
ORDER MULTIPLE FEEDBACK LOW-PASS FILTER
Figure 69 shows the LMH6619 used as the amplifier in a multiple feedback low pass filter. This filter is set up to
have a gain of +1 and a −3 dB point of 1 MHz. Values can be determined by using the WEBENCH
®
Active Filter
Designer found at webench.ti.com.
Figure 69. 4
th
Order Multiple Feedback Low-Pass Filter
CURRENT SENSE AMPLIFIER
With it’s rail-to-rail input and output capability, low V
OS
, and low I
B
the LMH6618 is an ideal choice for a current
sense amplifier application. Figure 70 shows the schematic of the LMH6618 set up in a low-side sense
configuration which provides a conversion gain of 2V/A. Voltage error due to V
OS
can be calculated to be V
OS
x
(1 + R
F
/R
G
) or 0.75 mV x 20.6 = 15.5 mV. Voltage error due to I
O
is I
O
x R
F
or 0.26 µA x 1 kΩ = 0.26 mV. Hence
total voltage error is 15.5 mV + 0.26 mV or 15.7 mV which translates into a current error of 15.7 mV/(2 V/A) = 7.9
mA.
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