OPA2830 Datasheet, PDF (27/43 Pages) National Semiconductor (TI) – Dual, Low-Power, Single-Supply, Wideband OPERATIONAL AMPLIFIER

OPA2830
www.ti.com.................................................................................................................................................. SBOS309D – AUGUST 2004 – REVISED AUGUST 2008
+V_S
+5V
374Ω
2.2nF 2.2nF
1/2
OPA2830
750Ω
2kΩ
1µF
V_I
V_S/2
V_O
2kΩ
750Ω
2.2nF 2.2nF
1/2
OPA2830
374Ω
compliance voltage other than ground for operation,
the appropriate voltage level may be applied to the
noninverting input of the OPA2830. The DC gain for
this circuit is equal to R_F. At high frequencies, the
DAC output capacitance (C_D in Figure 83) will
produce a zero in the noise gain for the OPA2830
that may cause peaking in the closed-loop frequency
response. C_F is added across R_F to compensate for
this noise gain peaking. To achieve a flat
transimpedance frequency response, the pole in each
feedback network should be set to:
Ǹ ¹
2pR_FC_F
+
GBP
4pR_FC_D
which will give a cutoff frequency f_–3dB of
approximately:
Ǹ f_*3dB +
GBP
2pR_FC_D
Figure 81. 138kHz, 2nd-Order, High-Pass Filter
Results showing the frequency response for the
circuit of Figure 81 is shown in Figure 82.
3
0
−3
−6
−9
−12
0.01
0.1
1
10
Frequency (MHz)
Figure 82. Frequency Response for the Filter of
Figure 81
+5V
High−Speed
DAC
I_O
2.5kΩ
C_D1
2.5kΩ
1/2
OPA2830
R_F1
C_F1
R_F2
V_O = I_O R_F
C_D2
C_F2
− I_O
+5V
2.5kΩ
1/2
OPA2830
−V_O = −I_O R_F
2.5kΩ
GBP →Gain Bandwidth
Product (Hz) for the OPA2830
HIGH-PERFORMANCE DAC
TRANSIMPEDANCE AMPLIFIER
High-frequency video Digital-to-Analog Converters
(DACs) can sometimes benefit from a low distortion
output amplifier to retain their SFDR performance into
real-world loads. Figure 83 shows a differential output
drive implementation. The diagram shows the signal
output current(s) connected into the virtual ground
summing junction(s) of the OPA2830, which is set up
as a transimpedance stage or I-V converter. If the
DAC requires that its outputs terminate to a
Figure 83. High-Speed DAC—Differential
Transimpedance Amplifier
Copyright © 2004–2008, Texas Instruments Incorporated
Product Folder Link(s): OPA2830
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