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參數(shù)資料
| 型號： | DAC2932PFBTG4 |
| 元件分類： | DAC |
| 英文描述： | DUAL 12-BIT 40MSPS DIGITAL TO ANALOG CONVERTER |
| 中文描述： | 雙通道12位40MSPS數(shù)模轉(zhuǎn)換器 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大?。?/td> | 343K |
| 代理商： | DAC2932PFBTG4 |
SBAS279C AUGUST 2003 REVISED OCTOBER 2004
www.ti.com
17
As shown in Figure 29, the transformer center tap is
connected to ground. This forces the voltage swing on
I
OUT
and I
OUT
to be centered at 0V. In this case the two
resistors, R
L
, may be replaced with one, R
DIFF
, or omitted
altogether. Alternatively, if the center tap is not connected,
the signal swing will be centered at R
L
×
I
OUTFS
/2.
However, in this case, the two resistors (R
L
) must be used
to enable the necessary dc-current flow for both outputs.
DAC2932
I
OUT
I
OUT
RF
Transformer
R
L
250
R
L
250
R
S
R
DIFF
Figure 29. Differential Output Configuration
Using an RF Transformer
DIFFERENTIAL CONFIGURATION USING AN OP AMP
If the application requires a dccoupled output, a difference
amplifier may be considered, as shown in Figure 30. Four
external resistors are needed to configure the OPA690
voltage-feedback op amp as a difference amplifier
performing the differential to single-ended conversion. Under
the configuration shown, the DAC2932 generates a
differential output signal of 0.5V
PP
at the load resistors, R
L
.
I
OUT
I
OUT
DAC2932
R
4
499
R
L
249
R
L
249
R
3
249
R
2
499
R
1
249
OPA690
C
OPT
+5V
V
OUT
5V
Figure 30. Difference Amplifier Provides
Differential-to-Single-Ended Conversion and
DC-Coupling
The OPA690 is configured for a gain of two. Therefore,
operating the DAC2932 with a 2mA full-scale output
produces a voltage output of
±
1V. This requires the
amplifier to operate from a dual power supply (
±
5V). The
tolerance of the resistors typically sets the limit for the
achievable common-mode rejection. An improvement can
be obtained by fine tuning resistor R
4
.
This configuration typically delivers a lower level of ac
performance than the previously discussed transformer
solution because the amplifier introduces another source
of distortion. Suitable amplifiers should be selected based
on their slew-rate, harmonic distortion, and output swing
capabilities. A high-speed amplifier like the OPA690 may
be considered. The ac performance of this circuit can be
improved by adding a small capacitor (C
DIFF
) between the
outputs I
OUT
and I
OUT
, as shown in Figure 30. This will
introduce a real pole to create a low-pass filter in order to
slew-limit the fast output signal steps of the DAC, which
otherwise could drive the amplifier into slew-limitations or
into an overload condition; both would cause excessive
distortion. The difference amplifier can easily be modified
to add a level shift for applications requiring the
single-ended output voltage to be unipolar (that is, swing
between 0V and +2V).
DUAL TRANSIMPEDANCE OUTPUT
CONFIGURATION
The circuit example of Figure 31 shows the signal output
currents connected into the summing junctions of the
OPA2690 dual voltage-feedback op amp, which is set up as
a transimpedance stage or I-to-V converter. With this circuit,
the DAC output will be kept at a virtual ground, minimizing the
effects of output impedance variations, which results in the
best dc linearity (INL). As mentioned previously, care should
be taken not to drive the amplifier into slew-rate limitations
and produce unwanted distortion.
1/2
OPA2690
1/2
OPA2690
DAC2932
V
OUT
= I
OUT
R
F
1
V
OUT
= I
OUT
R
F
2
R
F1
R
F2
C
F1
C
F2
C
D1
C
D2
I
OUT
I
OUT
50
50
5V
+5V
Figure 31. The OPA2690 Dual, Voltage-Feedback
Amplifier Forms a Transimpedance Amplifier
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| DAC2932 | DUAL 12-BIT 40MSPS DIGITAL TO ANALOG CONVERTER |
| DAC2932PFBR | DUAL 12-BIT 40MSPS DIGITAL TO ANALOG CONVERTER |
| DAC2932PFBT | DUAL 12-BIT 40MSPS DIGITAL TO ANALOG CONVERTER |
| DAC312BR | 12-Bit Digital-to-Analog Converter |
| DAC312GBC | 12-Bit Digital-to-Analog Converter |
相關(guān)代理商/技術(shù)參數(shù) |
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| DAC2KY | 制造商:BB 制造商全稱:BB 功能描述:Dual, 12-Bit, 125MSPS DIGITAL-TO-ANALOG CONVERTER |
| DAC312 | 制造商:AD 制造商全稱:Analog Devices 功能描述:12-Bit High Speed Multiplying D/A Converter |
| DAC312BR | 制造商:Rochester Electronics LLC 功能描述:12-BIT HIGH-SPEED MULTIPL - Bulk |
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