ADI AD538BD

The AD538 is a monolithic real-time computing circuit that performs accurate analog multiplication, division, and power-of functions. Low input and output offset voltages combined with excellent linearity enable accurate computation over an exceptionally wide input dynamic range. Laser wafer trimming reduces multiplication and division errors to as low as 0.25% of reading, with a typical output offset of 100 μV or less, further enhancing overall off-the-shelf performance. The device's 400 kHz bandwidth further strengthens real-time analog signal processing capability.

The overall transfer function of the AD538 is VO = VY(VZ/VX)m. Specific functions are programmed via pin connections. Single-quadrant (positive input) multiplication and division require no external components. Two-quadrant (bipolar numerator) division is achieved using external level shifting and scaling resistors. The required scale factor for multiplication and division can be set using the on-chip +2V or +10V reference, or controlled externally for simultaneous multiplication and division. Adding one or two external resistors enables power-of functions with m values ranging from 0.2 to 5.

Direct log-ratio computation is possible using only the log-ratio and output sections of the chip. Access to multiple summing nodes further enhances the flexibility of the AD538. Finally, a wide supply voltage range of ±4.5 V to ±18 V accommodates standard ±5 V, ±12 V, and ±15 V supplies.

The AD538 is available in two accuracy grades (A and B) for the industrial temperature range (-25°C to +85°C), and one grade (S) for the temperature range (-55°C to +125°C). The device is offered in an 18-pin TO-118 hermetic side-brazed ceramic DIP package. Die in grade A is also available.

• ∇V₀ = Vv(Vz/Vx)ᵐ transfer function
• Wide dynamic range (denominator) −1000:1
• Simultaneous multiplication and division
• Resistor-programmable power and root
• No external trimming required
• Low input offset < 100 μV
• Low error, ±0.25% of reading (100:1 range)
• Monolithic construction
• Real-time analog multiplication, division, and exponentiation
• High-accuracy analog division with wide input dynamic range
• On-chip +2 V or +10 V scaling reference voltage
• Voltage and current (summing) input modes
• Lower cost and higher reliability vs. hybrid and modular circuits with monolithic construction

• Single-quadrant or two-quadrant multiply/divide operations
• Logarithmic ratio computation
• Square/square root operations
• Trigonometric function approximation
• Linearization via curve fitting
• Precision automatic gain control
• Power function operations