Analog Devices AD602, AD600 manual 0dB Adjust

Page 16

AD600/AD602

C1LO

A1HI

A1LO

GAT1

GAT2

A2LO

A2HI

C2LO

0dB ADJUST

 

 

 

 

 

 

1

 

 

 

 

16

 

 

 

 

 

 

2

 

 

A1

15

 

 

 

 

 

 

3

 

 

 

 

14

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

REF

 

13

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

12

 

 

 

 

 

 

6

 

 

A2

11

 

 

 

 

 

 

7

 

 

 

 

10

 

 

 

 

 

 

 

 

 

 

 

 

8

U1 AD600

9

 

 

C1HI

 

A1CM

C1

 

A1OP

0.1F

VPOS

+6V DEC

R1

VNEGΩ

–6V DEC 133k

A2OP

A2CM

C2HI

R2

100Ω

U3A

1/4

AD713

C2 R5

0.1FΩ

5.36k

R4 C3

133kΩ 0.001F

C1LO

A1HI

A1LO

GAT1

GAT2

A2LO

A2HI

U3B

C2LO

1/4

AD713

1

16

C1HI

 

 

 

 

 

2

15

A1CM

C4

 

 

VOUT

A1

14

A1OP

2F

3

 

 

 

4

13

VPOS

+6V DEC

 

 

 

REF

12

VNEG

–6V DEC

 

5

 

 

6

11

A2OP

 

 

A2

10

A2CM

 

 

7

 

 

 

 

 

8

9

C2HI

 

 

 

 

 

U2 AD600

R3

 

 

 

 

 

+6V

 

 

 

 

 

 

 

R17

INPUT

 

 

 

 

R6

 

R7

R8

R9

R16

 

200Ω

 

 

 

 

 

 

115Ω

 

 

 

 

3.4kΩ

 

1kΩ

294Ω

1kΩ

287Ω

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C5

 

 

 

 

 

 

+6V

 

 

 

 

 

 

22F

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+6V DEC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FB

 

 

 

 

 

 

 

 

 

 

 

 

 

0.1F

 

 

 

 

 

 

 

 

 

 

 

 

 

+6V DEC

 

 

 

 

 

1

VINP

VPOS

14

 

 

 

 

 

 

 

 

 

NC

2

U4

 

13

NC

 

 

 

–6V DEC

 

 

 

 

AD636

 

R11

 

 

 

 

 

 

 

0.1F

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

56.2kΩ

 

 

 

 

 

–6V DEC

3

VNEG

 

12

NC

 

 

FB

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

CAVG

 

11

NC

R10

 

C6

 

 

 

 

 

 

 

4.7F

 

 

 

 

 

 

 

3.16kΩ

–6V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NC

5

VLOG

COMM

10

 

 

 

 

POWER SUPPLY

 

 

 

 

NC

6

BFOP

LDLO

9

 

 

 

 

DECOUPLING NETWORK

 

 

 

 

 

 

 

 

 

 

 

+6V DEC

 

 

7

BFIN

VRMS

8

 

 

U3C

VLOG

 

 

 

 

 

 

 

 

 

R15

 

 

 

 

 

 

 

 

 

1/4

 

 

 

5.11kΩ

 

 

 

 

 

 

 

+316.2mV

 

AD713

 

 

 

R14

R13

R12

 

 

 

 

 

 

NC = NO CONNECT

 

 

 

7.32kΩ

866Ω

1kΩ

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 29. 120 dB Dynamic Range RMS Responding Circuit Optimized for S/N Ratio

resistance of U1A as well as the fixed 6 dB attenuation provided by R2 and the input resistance of U1B are included both to set

VLOG to read 0 dB when VIN is 3.16 mV rms and to center the 100 dB range between 10 μV rms and 1 V rms input. R5 and

C3 provide a 3 dB noise bandwidth of 30 kHz. R12 to R15 change the scaling from 625 mV/decade at the control inputs to 1 V/decade at the output and at the same time center the dy- namic range at 60 dB, which occurs if the VG of U1B is equal to zero. These arrangements ensure that the VLOG will still fit within the ± 6 V supplies.

Figure 30 shows VLOG to be linear over a full 120 dB range. Figure 31 shows the error ripple due to the individual gain func- tions which is bounded by ± 0.2 dB (dotted lines) from 6 μV to 2 V. The small perturbations at about 200 μV and 20 mV, caused by the impracticality of matching the gain functions per- fectly, are the only sign that the gains are now sequential. Fig-

ure 32 is a plot of VAGC which remains very close to its set value of 316 mV rms over the full 120 dB range.

To more directly compare the signal-to-noise ratios in the “simultaneous” and “sequential” modes of operation, all inter- stage attenuation was eliminated (R2 and R3 in Figure 25, R2 in Figure 29), the input of U1A was shorted, R5 was selected to provide a 20 kHz bandwidth (R5 = 7.87 kΩ), and only the gain control was varied, using an external source. The rms value of the noise was then measured at VOUT and expressed as an S/N

 

5

 

 

 

 

 

 

 

 

 

 

 

Volts–

4

 

 

 

 

 

2

 

 

 

 

 

 

3

 

 

 

 

 

OUTPUT

1

 

 

 

 

 

 

 

 

 

 

 

LOGARITHMIC

0

 

 

 

 

 

–3

 

 

 

 

 

 

–1

 

 

 

 

 

 

–2

 

 

 

 

 

 

–4

 

 

 

 

 

 

–5

 

 

 

 

 

 

 

 

 

 

 

 

1V

10V 100V 1mV 10mV 100mV

1V

10V

INPUT SIGNAL – V RMS

Figure 30. VLOG Is Essentially Linear Over the Full 120 dB Range

ratio relative to 0 dBV, this being almost the maximum output capability of the AD600. Results for the simultaneous mode can be seen in Figure 33. The S/ N ratio degreades uniformly as the gain is increased. Note that since the inverting gain control was used, the gain in this curve and in Figure 34 decreases for more positive values of the gain-control voltage.

–16–

REV. A

Image 16
Contents Functional Block Diagram Product DescriptionREV. a Connection Diagram Absolute Maximum RATINGS1Ordering Guide PIN DescriptionTheory of Operation Noise PerformanceSignal-Gating Inputs Sequential Mode Maximum S/N RatioGain-Control Interface Common-Mode RejectionParallel Mode Simplest Gain-Control Interface Where VC is the applied control voltageLow Ripple Mode Minimum Gain Error AD600/AD602 Applications Table I. Measured Preamplifier Performance Low Noise, 6 dB PreamplifierLow Noise AGC Amplifier with 80 dB Gain Range AD600/AD602 AD600/AD602 U1 AD600 DB Output of ’s Circuit Is Linear Over an 80 dB Range RMS Responding AGC Circuit with 100 dB Dynamic Range Gain Error for Without the 2 dB Offset Modification DB RMS/AGC System with Optimal S/N Ratio Sequential Gain0dB Adjust AD600/AD602 AD600/AD602-Typical Performance Characteristics Gating Feedthrough to Output, Gating Off to On Outline Dimensions Pin Plastic DIP N-16 PackagePin Soic R-16 Package Pin Cerdip Q-16 Package

AD600, AD602 specifications

Analog Devices, a leader in high-performance signal processing, offers the AD602 and AD600, two versatile RF amplifiers known for their impressive performance in a variety of applications. The AD602 is a dual-channel, low-noise variable gain amplifier (VGA), while the AD600 is a similar VGA but designed for single-channel applications. Both devices are highly regarded in the fields of communications, instrumentation, and imaging, as they provide outstanding performance in amplifying weak signals.

The AD602 features a gain range of -6 dB to +40 dB, allowing for precise control of the output signal strength. This flexibility makes it well-suited for applications such as IF amplification, where signal levels can vary significantly. The device also includes a low distortion characteristic, enabling it to maintain signal integrity even when handling larger input signals. With a wide bandwidth spanning from DC to 100 MHz, the AD602 caters to applications requiring both low-frequency and high-frequency performance.

On the other hand, the AD600 shares many similarities with the AD602 but offers slightly different characteristics. With a gain range of -1.5 dB to +40 dB, it offers a broader range of control for its output signal strength. Like the AD602, its low distortion and high linearity are crucial for high-fidelity signal processing. The AD600 is also capable of delivering a high output current, making it favorable for driving capacitive loads effectively.

Both devices employ Analog Devices' proprietary topology that minimizes the effects of thermal drift and achieves high levels of performance under varying conditions. They are built with advanced manufacturing processes that ensure stability and reliability in industrial applications. Integrated with differential inputs, these devices help eliminate common-mode noise, thus improving overall signal quality.

The AD602 and AD600 are equipped with comprehensive protection features, enabling them to withstand overload conditions without compromising performance. Their low noise figure contributes to excellent low-level signal recovery, making these amplifiers ideal for radar receivers, medical imaging systems, and satellite communication.

In summary, the AD602 and AD600 by Analog Devices stand out as powerful, reliable variable gain amplifiers with robust performance characteristics. Their flexibility in gain control, low distortion, high linearity, and advanced protection features make them invaluable components in modern electronic systems, enhancing the quality and reliability of signal processing applications across various industries.