ad834.pdf

500 MHz Four-Quadrant Multiplier

AD834

FEATURES

DC to >500 MHz Operation

Differential 6 1 V Full-Scale Inputs

Differential 6 4 mA Full-Scale Output Current

Low Distortion ( £ 0.05% for 0 dBm Input)

Supply Voltages from 6 4 V to 6 9 V

Low Power (280 mW typical at V S = 6 5 V)

APPLICATIONS

High Speed Real Time Computation

Wideband Modulation and Gain Control

Signal Correlation and RF Power Measurement

Voltage Controlled Filters and Oscillators

Linear Keyers for High Resolution Television

Wideband True RMS

FUNCTIONAL BLOCK DIAGRAM

(W)

PRODUCT DESCRIPTION

The AD834 is a monolithic laser-trimmed four-quadrant analog

multiplier intended for use in high frequency applications, hav-

ing a transconductance bandwidth (R L = 50 W) in excess of

500 MHz from either of the differential voltage inputs. In multi-

plier modes, the typical total full-scale error is 0.5%, dependent

on the application mode and the external circuitry. Performance

is relatively insensitive to temperature and supply variations, due

to the use of stable biasing based on a bandgap reference genera-

tor and other design features.

To preserve the full bandwidth potential of the high speed

bipolar process used to fabricate the AD834, the outputs appear

as a differential pair of currents at open collectors. To provide a

single ended ground referenced voltage output, some form of ex-

ternal current to voltage conversion is needed. This may take the

form of a wideband transformer, balun, or active circuitry such

as an op amp. In some applications (such as power mea-

surement) the subsequent signal processing may not need to

have high bandwidth.

The transfer function is accurately trimmed such that when

X = Y = ± 1 V, the differential output is ± 4 mA. This absolute

calibration allows the outputs of two or more AD834s to be

summed with precisely equal weighting, independent of the

accuracy of the load circuit.

The AD834J is specified for use over the commercial tempera-

ture range of 0°C to +70°C and is available in an 8-pin DIP

package and an 8-pin plastic SOIC package. AD834A is avail-

able in cerdip for operation over the industrial temperature

range of –40°C to +85°C. The AD834S/883B is specified for

operation over the military temperature range of –55°C to

+125°C and is available in the 8-pin cerdip package. S-Grade

chips are also available.

Two application notes featuring the AD834 (AN-212 and

AN-216) can now be obtained by calling 1-800-ANALOG-D.

For additional applications circuits consult the AD811 data

sheet.

PRODUCT HIGHLIGHTS

l. The AD834 combines high static accuracy (low input and

output offsets and accurate scale factor) with very high band-

width. As a four-quadrant multiplier or squarer, the response

extends from dc to an upper frequency limited mainly by

packaging and external board layout considerations. A large

signal bandwidth of over 500 MHz is attainable under opti-

mum conditions.

2. The AD834 can be used in many high speed nonlinear

operations, such as square rooting, analog division, vector

addition and rms-to-dc conversion. In these modes, the

bandwidth is limited by the external active components.

3. Special design techniques result in low distortion levels (bet-

ter than –60 dB on either input) at high frequencies and low

signal feedthrough (typically –65 dB up to 20 MHz).

4. The AD834 exhibits low differential phase error over the in-

put range—typically 0.08° at 5 MHz and 0.8° at 50 MHz.

The large signal transient response is free from overshoot,

and has an intrinsic rise time of 500 ps, typically settling to

within 1% in under 5 ns.

5. The nonloading, high impedance, differential inputs simplify

the application of the AD834.

REV. B

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

AD834–SPECIFICATIONS (T A = +25 8 C and 6 V S = 6 5 V, unless otherwise noted; dBm assumes 50 V load.)

AD834J

AD834A, S

Model

Conditions

Min Typ

Max

Min

Typ

Max

Units

MULTIPLIER PERFORMANCE

Transfer Function

(1 V ) 2

´ 4 mA

(1 V ) 2

´ 4 mA

Total Error 1 (Figure 6)

–1 V £ X, Y < +1 V

± 0.5

6 2

± 0.5

6 2

% FS

vs. Temperature

T MIN to T MAX

± 1.5

6 3

% FS

vs. Supplies 2

± 4 V to ± 6 V

0.1

0.3

0.1

0.3

% FS/V

Linearity 3

± 0.5

6 1

± 0.5

6 1

% FS

Bandwidth 4

See Figure 5

500

MHz

Feedthrough, X

X = ± 1 V, Y = Nulled

0.2

0.3

0.2

0.3

% FS

Feedthrough, Y

X = Nulled, Y = ± 1 V

0.1

0.2

0.1

0.2

% FS

AC Feedthrough, X 5

X = 0 dBm, Y = Nulled

f = 10 MHz

–65

f = 100 MHz

–50

AC Feedthrough, Y 5

X = Nulled, Y = 0 dBm

f = 10 MHz

–70

f = 100 MHz

–50

INPUTS (X1, X2, Y1, Y2)

Full-Scale Range

Differential

± 1

Clipping Level

Differential

1.1

1.3

1.1

1.3

Input Resistance

Differential

Offset Voltage

0.5

vs. Temperature

T MIN to T MAX

mV/°C

vs. Supplies 2

± 4 V to ± 6 V

100

300

100

300

mV/V

Bias Current

Common-Mode Rejection

f £ 100 kHz; 1 V p-p

Nonlinearity, X

Y = 1 V; X = ± 1 V

0.2

0.5

0.2

0.5

% FS

Nonlinearity, Y

X = 1 V; Y = ± 1 V

0.1

0.3

0.1

0.3

% FS

Distortion, X

X = 0 dBm, Y = 1 V

f = 10 MHz

–60

f = 100 MHz

–44

Distortion, Y

X = 1 V, Y = 0 dBm

f = 10 MHz

–65

f = 100 MHz

–50

OUTPUTS (W1, W2)

Zero Signal Current

Each Output

8.5

Differential Offset

X = 0, Y = 0

± 20

6 60

± 20

6 60

vs. Temperature

T MIN to T MAX

nA/

6 60

Scaling Current

Differential

3.96 4

4.04

3.96

4.04

Output Compliance

4.75

Noise Spectral Density

f = 10 Hz to 1 MHz

nV/

ÖHz

Outputs into 50 W Load

POWER SUPPLIES

Operating Range

± 4

± 9

± 4

± 9

Quiescent Current 6

T MIN to T MAX

+V S

–V S

TEMPERATURE RANGE

Operating, Rated Performance

Commercial (0°C to +70°C)

AD834J, JR-REEL

Military (–55°C to +125°C)

AD834S

Industrial (–40°C to +85°C)

AD834A

PACKAGE OPTIONS

8-Pin SOIC (R)

AD834JR

8-Pin Cerdip (Q)

AD834AQ

8-Pin Plastic DIP (N)

AD834JN

AD834SQ/883B

10 kHz.

3 Linearity is defined as residual error after compensating for input offset voltage, output offset current and scaling current errors.

4 Bandwidth is guaranteed when configured in squarer mode. See Figure 5.

5 Sine input; relative to full-scale output; zero input port nulled; represents feedthrough of the fundamental.

6 Negative supply current is equal to the sum of positive supply current, the signal currents into each output, W1 and W2, and the input bias currents.

Specifications in boldface are tested on all production units at final electrical test. Results from those tests are used to calculate outgoing quality levels.

Specifications subject to c hange without notice.

–2–

REV. B

NOTES

1 Error is defined as the maximum deviation from the ideal output, and expressed as a percentage of the full-scale output.

2 Both supplies taken simultaneously; sinusoidal input at f

AD834

ABSOLUTE MAXIMUM RATINGS*

Supply Voltage (+V S to –V S ) . . . . . . . . . . . . . . . . . . . . . . 18 V

Internal Power Dissipation . . . . . . . . . . . . . . . . . . . . . 500 mW

Input Voltages (X1, X2, Y1, Y2) . . . . . . . . . . . . . . . . . . . . +V S

Operating Temperature Range

AD834J . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C

AD834A . . . . . . . . . . . . . . . . . . . . . . . . . . . –40°C to +85°C

AD834S/883B . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C

Storage Temperature Range (Q) . . . . . . . . . –65°C to +150°C

Storage Temperature Range (R, N) . . . . . . . –65°C to +125°C

Lead Temperature (Soldering 60 sec) . . . . . . . . . . . . +300°C

ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500 V

*Stresses above those listed under “Absolute Maximum Ratings” may cause

permanent damage to the devices. This is a stress rating only and functional

operation of the device at these or any other conditions above those indicated in the

operational section of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

THERMAL CHARACTERISTICS

u JC

CONNECTION DIAGRAM

Small Outline (R) Package

Plastic DIP (N) Package

Cerdip (Q) Package

u JA

METALIZATION PHOTOGRAPH

CHIP DIMENSIONS AND BONDING DIAGRAM

Dimensions shown in inches and (mm).

Contact factory for latest dimensions.

8-Pin Cerdip Package (Q)

30°C/W

110°C/W

8-Pin Plastic SOIC (R)

45°C/W

165°C/W

8-Pin Plastic Mini-DIP (N )

50°C/W

99°C/W

ORDERING GUIDE

Temperature

Package

Model

Range

Option*

AD834JN

C to +70

N-8

AD834JR

0°C to +70°C

R-8

AD834JR-REEL

C to +70

R-8

AD834AQ

–40

C to +85

Q-8

AD834SQ/883B

–55°C to +125°C

Q-8

AD834S Chips

Chips

*N = Plastic DIP; Q = Cerdip; R = Small Outline IC (SOIC) Package.

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

Small Outline (R) Package

Cerdip (Q) Package

REV. B

–3–

AD834–Typical Characteristics

Figure 1. Mean-Square Output

vs. Frequency

Figure 2. AC Feedthrough

vs. Frequency

Figure 3. Total Harmonic Distortion

vs. Frequency

Figure 1. Figure 1 is a plot of the mean-square output versus

frequency for the test circuit of Figure 5. Note that the rising

response is due to package resonances.

Figure 2. For frequencies above 1 MHz, ac feedthrough is

dominated by static nonlinearities in the transfer function and

the finite offset voltages. The offset voltages cause a small frac-

tion of the fundamental to appear at the output, and can be

nulled out.

Figure 3. THD data represented in Figure 3 is dominated by

the second harmonic, and is generated with 0 dBm input on the

ac input and +1 V on the dc input. For a given amplitude on the

ac input, THD is relatively insensitive to changes in the

dc input amplitude. Varying the ac input amplitude while

maintaining a constant dc input amplitude will affect THD

performance.

By placing capacitors C3/C5 and C4/C6 across load resistors R1

and R2, a simple low-pass filter is formed, and the mean-square

value is extracted. The mean-square response can be measured

using a DVM connected across R1 and R2.

Figure 5. Bandwidth Test Circuit

Figure 4. Test Configuration for Measuring AC

Feedthrough and Total Harmonic Distortion

Figure 5. The squarer configuration shown in Figure 5 is used

to determine wideband performance because it eliminates the

need for (and the response uncertainties of) a wideband mea-

surement device at the output. The wideband output of a

squarer configuration is a fluctuating current at twice the input

frequency with a mean value proportional to the square of the

input amplitude.

Figure 6. Low Frequency Test Circuit

–4–

REV. B

AD834

BASIC OPERATION

Figure 7 is a functional equivalent of the AD834. There are

three differential signal interfaces: the voltage inputs X =

X1–X2 and Y = Y1–Y2, and the current output, W (see Figure

7) which flows in the direction shown when X and Y are posi-

tive. The outputs W1 and W2 each have a standing current of

typically 8.5 mA.

A can generate significant offset voltages if not

compensated. For example, with a source and termination

resistance of 50 W (net source of 25 W) the offset would be

Figure 7. AD834 Functional Block Diagram

The input voltages are first converted to differential currents

which drive the translinear core. The equivalent resistance of

the voltage-to-current (V-I) converters is about 285 W. This low

value results in low input related noise and drift. However, the

low full-scale input voltage results in relatively high nonlinearity

in the V-I converters. This is significantly reduced by the use of

distortion cancellation circuits which operate by Kelvin sensing

the voltages generated in the core—an important feature of the

AD834.

The current mode output of the core is amplified by a special

cascode stage which provides a current gain of nominally ´ 1.6,

trimmed during manufacture to set up the full-scale output cur-

rent of ± 4 mA. This output appears at a pair of open col-

lectors which must be supplied with a voltage slightly

above the voltage on Pin 6. As shown in Figure 8, this can be

arranged by inserting a resistor in series with the supply to this

pin and taking the load resistors to the full supply. With R3 =

60 W, the voltage drop across it is about 600 mV. Using two

50 W load resistors, the full-scale differential output voltage is

± 400 mV.

The full bandwidth potential of the AD834 can only be realized

when very careful attention is paid to grounding and decou-

pling. The device must be mounted close to a high quality

ground plane and all lead lengths must be extremely short, in

keeping with UHF circuit layout practice. In fact, the AD834

shows useful response to well beyond 1 GHz, and the actual up-

per frequency in a typical application will usually be determined

by the care with which the layout is effected. Note that R4 (in

series with the –V S supply) carries about 30 mA and thus intro-

duces a voltage drop of about 150 mV. It is made large enough

to reduce the Q of the resonant circuit formed by the supply

lead and the decoupling capacitor. Slightly larger values can be

used, particularly when using higher supply voltages. Alterna-

tively, lossy RF chokes or ferrite beads on the supply leads may

be used.

Figure 8 shows the use of optional termination resistors at the

inputs. Note that although the resistive component of the input

A = 1.125 mV. This can be almost fully cancelled by

including (in this example) another 25 W resistor in series with

the “unused” input (in Figure 8, either X1 or Y2). In order to

minimize crosstalk the input pins closest to the output (X1 and

Y2) should be grounded; the effect is merely to reverse the

phase of the X input and thus alter the polarity of the output.

TRANSFER FUNCTION

The output current W is the linear product of input voltages

X and Y divided by (1 V) 2 and multiplied by the “scaling

current” of 4 mA:

()

2 4 mA

Provided that it is understood that the inputs are specified in

volts, a simplified expression can be used:

250 W

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 will then be very high.

1 V ´

TRANSFORMER COUPLING

In many high frequency applications where baseband operation

is not required at either inputs or output, transformer coupling

can be used. Figure 9 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 de-

sired load impedance by appropriate choice of turns ratio. The

specific choice of the transformer design will depend entirely on

the application. Transformers may also be used at the inputs.

Center-tapped transformers can reduce high frequency distor-

tion and lower HF feedthrough by driving the inputs with bal-

anced signals.

REV. B

–5–

Figure 8. Basic Connections for Wideband Operation

impedance is quite high (about 25 kW), the input bias current of

typically 45

1 V

( XY )4 mA

Alternatively, the full transfer function can be written:

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: