DA1822A and DA1820A
DISCONTINUED
PRODUCTS
Leading
Features
-
DC
to 10 MHz Bandwidth
-
100,000
to 1 CMRR
-
Gain
of 1, 10, 100 & 1000
-
Full
Upper & Lower Bandwidth Limits
The
DA1820A/1822 is a stand-alone, high-performance 10 MHz
differential amplifier. It is intended to act as a
signal conditioning preamplifier for oscilloscopes and network
and spectrum analyzers, providing differential measurement
capability to instruments having only a single-ended input.
Amplifier
gain can be set to 1, 10, 100 or 1000. The high gain of the
DA1822A can extend the sensitivity of a scope with 2 mV/div to
2 µV/div. A built-in input attenuator can be separately set
to attenuate signals by a factor of 10, allowing gains of
1000, 100, 10, 1, or 0.1 and common mode dynamic range of
±15.5 V (÷1) or ±155 V (÷10). Optional probes further
increase the maximum input signal and common mode ranges in
proportion to their attenuation ratio, but not exceeding the
probe's maximum input voltage rating. Effective gain of the
DA1822A, including probe attenuation, amplifier gain and
attenuator settings, is automatically displayed.
The
DA1820A/1822 have a bandwidth of DC to 10 MHz, but the
operator can select from a full complement of high- and
low-frequency -3 dB points. In critical measurements, the
signal-to-noise ratio can be greatly improved by restricting
the amplifier bandwidth to the frequency range of interest.
The
DA1822A features a built-in Precision Voltage Generator (PVG)
that can be set to any voltage between ±15.5 volts (±10
volts in Differential Offset) with up to 51/2
digit resolution. The PVG's output can be selected as
an input to the inverting (-) input of the amplifier for
operation as a differential comparator or applied internally
as a true differential offset voltage. The voltage is also
available to be used externally through a rear panel
connector. The PVG is not included in the model 1820.
The
DA1820A/1822 operate from 100 to 250 V AC line without line
switching. A wide range of high-performance differential
probes are available for use with the DA1820A/1822. These include the DXC100A selectable (÷10/÷100) attenuation
probes, the DXC350A ÷100 high-impedance (92 meg/2.4 pF) probe
and the ÷1 DXC200A probes.
Comparator
Mode (DA1822A only)
The
DA1822A becomes a differential comparator when the internal
Precision Voltage Generator (PVG) output is selected as the
amplifier's inverting (-) input. In this mode, the DA1822A can
be used to very accurately measure relatively small signals
that are riding on large AC or DC components. Due to the
precision and 51/2 digit resolution of
the voltage generator, an oscilloscope, when used with the
DA1822A, can make voltage measurements that are much more
accurate than the oscilloscope is capable of by itself. The
output of the PVG is available for external use via a
rear-panel connector. When used in the comparison mode, the
DA1822A's "-" Input is connected to the output of
the PVG, and the DA1822A's "-" Input probe is no
longer used. The operator can then use the PVG as a very
accurate position or offset control to compare to the PVG's
value with any point on the "+" Input signal. The
decimal point in the PVG readout is automatically positioned
to account for the DA1822A's attenuator and any probe
attenuation.
True
Differential Offset Mode
The
built-in PVG can be used to generate a true differential
offset while still allowing both inputs to be used as
differential inputs. Operation in the differential offset mode
is very similar to that of the comparison mode, except the
"-" Input of the DA1820A/1822 is still functional.
In this mode, the output of the PVG is used to generate an
offset within the DA1822A's amplifier (an external voltage can
be supplied to the DA1820A). The PVG now functions as if a
zero impedance adjustable voltage source were placed in series
with the "-" Input. The decimal point in the PVG
readout is automatically placed to account for DA1822A
attenuator and probe attenuation factors as well as the
DA1822A's gain setting.
This
mode facilitates making measurements such as changes to a
transistor's base to emitter voltage caused by variations in
temperature and/or current. Used in this mode, the voltage
generator can be set to a value that will zero out the static
value of the junction's on voltage. The DA1822A's differential
measurement capability will reject any dynamic signal common
to both sides of the junction, and the oscilloscope is left to
measure only the changes in the junction
voltage.
Precision
Voltage Generator (DA1822A only)
The
Precision Voltage Generator is controlled from the
oscilloscope offset knob. Each digit can be individually incremented or
decremented and rollover automatically carries to the next
digit. The range of the
generator is ±15.5 V for the comparator mode and ±10.0 V for
differential offset mode. This range is multiplied by
the attenuation factor of the probes and internal
attenuator. The generator's temperature-controlled
oven allows for a DC accuracy specification of 0.05% +500 µV.
The
DA1820A/1822 input is protected to ±250 V and will
automatically disconnect large signals.
Upper
& Lower Bandwidth Limits
The
DA1820A/1822 allows the user to select both the upper and
lower frequency -3 dB points. Selections for the high
frequency -3 dB points are 3 MHz, 1 MHz, 300 kHz, 100 kHz, 30
kHz, 10 kHz, 3 kHz, 1 kHz, 300 Hz, and 100 Hz. Selections for
the lower frequency -3 dB points are
0.1 Hz, 1 Hz, 10 Hz, 100 Hz, and 1 kHz. These filters make it
possible to improve the signal-to-noise ratio when making
measurements on microvolt magnitude signals.
Autobalance
Each
time any of the gain buttons is pressed, the DA1820A/1822
adjusts the amplifiers DC balance.
Specifications
| General |
|
Amplifier
gain:
|
1, 10, 100 or 1000 |
|
Gain
accuracy:
|
±1% +
uncertainty of termination resistance |
|
Bandwidth:
|
(x1
or x10 GAIN) DC to 10 MHz
(x100 GAIN) DC to 3 MHz
(x1000 GAIN) DC to 1 MHz |
|
Risetime:
|
(x1 or x10 GAIN) <35 ns |
|
Output
impedance:
|
50 ohm |
|
Intended
output load:
|
50 ohm |
|
Maximum
output:
|
limited at ±5 V into 50 ohm |
|
Input
attenuation:
|
÷1 or ÷10 |
| ÷10
Attenuator accuracy: |
±0.05% |
| Max
differential linear input: |
5V
|
x
(combined internal and probe's attenuation
factor) |
| Gain
Setting |
|
|
Input
noise (x10 GAIN):
|
< 9
nV/sqrt Hz, broadband |
|
DC
drift (x10 GAIN):
|
50 µV/°C |
|
Common
mode rejection ratio:
|
See graph on previous page. |
|
Max
common mode input range:
|
(÷1
Attenuator): ±15.5 V
(÷10 Attenuator): ±155 V
(÷10 Attenuator and x10 probe): ±1.55 kV |
| Input
resistance |
| (÷1
Attenuator): |
1 M(ohm) or 100 M(ohm) |
|
(÷10 Attenuator and/or with attenuating probe
attached): |
1 M(ohm) |
|
Input capacitance (÷1 or ÷10 Attenuator): |
20 pF |
|
Bandwidth
limit filters
|
|
Upper:
|
3 MHz, 1 MHz, 300 kHz, 100 kHz, 30
kHz, 10 kHz, 3 kHz, 1 kHz, 300 Hz and 100 Hz |
|
Lower:
|
0.1 Hz, 1 Hz, 10 Hz, 100 Hz and 1 kHz |
|
Filter
characteristics:
|
6 dB/octave |
|
+
Input selections:
|
AC, OFF (precharge), DC |
|
-
Input selections:
|
AC, OFF (precharge), DC, VCOMP |
| Input
coupling capacitor: |
0.1 µF,400 V DC |
|
Input
gate current (x1 and x10 GAIN, ÷1 Attenuator):
|
<10 pA, 0-45°C |
| Input
protection: |
protected to ± 250 V, automatic input
disconnect with manual reset. |
Differential
Offset (VDIFF) Mode
|
|
Differential
offset range (referred to input):
|
|
(x10
GAIN or higher,÷1 Attenuator):
|
±1 V |
|
(x1
GAIN, ÷1 Attenuator):
|
±10 V |
|
(x10
GAIN or higher, ÷10 Attenuator):
|
±10 V |
(x1
GAIN, ÷10 Attenuator):
|
±100 V |
|
(x1
GAIN, ÷10 Attenuator, x10 probe):
|
±1.0 kV |
| Differential
Offset Accuracy |
|
(x10
GAIN or higher, ÷1 Attenuator):
|
0.1% + 50 µV |
|
(x1
GAIN, ÷1 Attenuator):
|
0.1% + 500 µV |
|
(x10
GAIN or higher,÷10 Attenuator):
|
0.15% + 500 µV |
| (x1
GAIN, ÷10 Attenuator): |
0.15% + 5 mV |
| Comparison
Offset (VCOMP) Mode |
| Effective
comparison voltage range (not effected by gain setting): |
|
(÷1 Attenuator): |
±15.5 V |
|
(÷10 Attenuator): |
±155 V |
|
(÷10 probe and ÷10 Attenuator): |
1.55 kV |
| Precision
Voltage Source |
| Output
range:
|
±15.5 V |
|
DC accuracy: |
0.05% of reading +500 µV (15°
to 45°C) |
|
Resolution:
|
up to 100 µV (51/2
digit) |
|
Temperature coefficient:
|
typically
<5 ppm/°C of full scale |
|
Type:
|
Oven stabilized buried zener. |
|
Output:
|
Applied to inverting input and
available at rear panel. |
|
Autozero: |
Sets output to zero when 0.0 volts
selected and periodically thereafter. |
| Power
Requirements |
| Line
voltage requirement: |
100 to 250 V AC |
|
Line frequency range: |
48 - 66 Hz |
|
Power requirement: |
~ 28 W,
~ 39 UA |
| |
|
| Environmental
Characteristics |
| Operating
Range: |
0° to 50°C |
|
Non-Operating: |
-4° to 75°C |
| |
|
| Physical
Characteristics |
| Height: |
7.29 cm (2.87") |
|
Width: |
21.2 cm (8.36") |
|
Depth: |
23.2 cm (9.12") |
|
Weight: |
2.15 kg (4.75 lb) |
|
Shipping Weight: |
3.12 kg (6.88 lb) |
| |
|
| Warranty: |
3 years |
| |
|
Ordering
Information
|
|
DA1822A;){kind=small}
;){kind=small}
DA18XX-RM01