AD834JRZ Analog Devices Inc, AD834JRZ Datasheet - Page 12

• Manufacturer Part Number: AD834JRZ
• Description: IC MULTIPLIER 4-QUADRANT 8-SOIC
• Manufacturer: Analog Devices Inc

Specifications of AD834JRZ

• Function: Analog Multiplier
• Number Of Bits/stages: 4-Quadrant
• Package / Case: 8-SOIC (3.9mm Width)
• No. Of Multipliers / Dividers: 1
• No. Of Amplifiers: 3
• Supply Voltage Range: ± 4V To �� 9V
• Operating Temperature Range: 0°C To +70°C
• Digital Ic Case Style: SOIC
• No. Of Pins: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD834
When both inputs are driven to their clipping level of about
1.3 V, the peak output current is roughly doubled to ±8 mA,
but distortion levels become very high.
BIASING THE OUTPUT
The AD834 has two open collector outputs as shown in Figure 13.
The +V
transistors. The following general guidelines maximize
performance of the AD834.
Figure 14 shows the currents at the input when the AD834
swings negative. Generally, +V
higher. For best performance, use resistor values that do not
saturate the output transistors. Allowing for adequate transistor
headroom reduces distortion.
When either output swings negative, the maximum current
flows through the RW resistors. It is in this situation that
headroom is at a minimum.
Headroom
Try to keep headroom at or above 200 mV to maintain adequate
range. Headroom ≥ 200 mV.
This recommendation addresses the positive swing of the
output as shown in Figure 15. It is sometimes difficult to meet
this for negative output swing.
NEGATIVE OUTPUT
SITUATION 1
VOTLAGE SWING
Headroom = Voltage at W
S
W1
pin, Pin 6, is tied to the base of the output NPN
NEGATIVE SWING
+5V
5
W BASE
12.5mA
RW
49.9Ω
Figure 13. Output Stage Block Diagram
OUTPUT OF AD834
MULTIPLIER
AD834
+5V
CORE
Figure 14. Negative Swing
W COLLECTOR
= (I
RW
+
HEADROOM
–
POS
49.9Ω
W2
SUPPLY × R
RW
S
COLLECTOR
should be biased at +4 V or
+5V
4
R
CC
+5V
− Voltage at W
+V
I
8.0mA TO 14mA
(GENERALLY 10.5mA)
POS
CC
R
75Ω
+V
CC
S
) − (12.5 mA × RW)
S
BIAS
+5V
SUPPLY
6
BASE
+V
–V
–5V
S
S
Rev. E | Page 12 of 20
The current through RW is smaller for positive output swings.
Headroom
For dc applications or applications where distortion is not a
concern, the headroom may be zero or as low as −200 mV.
However, for most cases, size the resistors to give the output
adequate headroom.
TRANSFORMER COUPLING
In many high frequency applications where baseband operation
is not required at either inputs or the output, transformer coupling
can be used. Figure 16 shows the use of a center-tapped output
transformer, which provides the necessary dc load condition
at the outputs, W1 and W2, and is designed to match into the
desired load impedance by appropriate choice of turns ratio.
The specific choice of the transformer design depends entirely
on the application. Transformers can also be used at the inputs.
Center-tapped transformers can reduce high frequency distortion
and lower HF feedthrough by driving the inputs with balanced
signals.
A particularly effective type of transformer is the balun
is a short length of transmission line wound onto a toroidal
ferrite core. Figure 17 shows this arrangement used to convert
the bal(anced) output to an un(balanced) one (therefore, the
use of the term). Although the symbol used is identical to that
for a transformer, the mode of operation is quite different. First,
1
For a good treatment of baluns, see Transmission Line Transformers by Jerry
Sevick; American Radio Relay League publication.
X-INPUT
Y-INPUT
±1V FS
±1V FS
SITUATION 2
POSITIVE OUTPUT
VOTLAGE SWING
POSITIVE SWING
W BASE
4.5mA
TERMINATION
RESISTOR
TERMINATION
RESISTOR
Figure 16. Transformer-Coupled Output
Figure 15. Positive Output Swing
+5V
X2
Y1
8
1
= (I
W COLLECTOR
RW
+
HEADROOM
–
49.9Ω
AD834
Y2 –V
X1 +V
4.7Ω
7
2
POS
SUPPLY × R
6
3
CERAMIC
S
S
CERAMIC
W2
W1
1µF
1µF
5
4
R
CC
+5V
+V
CC
I
8.0mA TO 14mA
(GENERALLY 10.5mA)
POS
) − (4.5 mA × RW)
S
SUPPLY
LOAD
+5V
1
–5V
, which