Part A
AD8304ARU
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 2030 PCS
- Series
- Linear - Amplifiers - Special Purpose Amplifiers
Replacement verdict
Not a drop-in replacement
The AD8309ARUZ and AD8304ARU are not drop-in replacements for one another. Although both are logarithmic amplifiers in the same TSSOP-16 package, they differ fundamentally in function: the AD8309ARUZ is a demodulating logarithmic amplifier with a limiter output, while the AD8304ARU is a logarithmic converter optimized for photodiode current measurement. Their input signal types, output formats, and application domains are distinct, so substituting one for the other requires circuit redesign and validation.
Different output type
Different input signal type
Different application function
Different output interface
Parts at a glance
Part B
AD8309ARUZ
Công ty Analog Devices Inc.
- Lifecycle
- Active
- Stock
- 6696 PCS
- Package
- TSSOP-16
- Series
- Linear - Amplifiers - Special Purpose
Key differences
Rows are prioritized by design impact. Highlighted values require attention during substitution.
Key electrical and mechanical differences between the two devices
| Parameter | AD8309ARUZ | AD8304ARU | Why it matters |
|---|---|---|---|
| Function | Logarithmic amplifier / RSSI (demodulating logarithmic amplifier) | Logarithmic converter (100 dB range logarithmic detector) | The core signal-processing function differs, so they are not direct functional substitutes in a given circuit. |
| Frequency Range | DC to 500 MHz | DC to 160 MHz | Operating bandwidth determines whether the part can handle the signal frequencies in the target application. |
| Dynamic Range | Approximately 100 dB | 100 dB (8 decades) | Dynamic range defines the span of input signal levels the device can accurately process. |
| Output Type | Logarithmic voltage output with limiter output | Logarithmic current/voltage output | Output format must match the downstream signal chain (ADC, comparator, or controller) for interchangeability. |
| Supply Voltage | 2.7 V to 5.5 V | 3.0 V to 5.5 V | Supply range affects compatibility with the system power rail and low-voltage operation. |
| Package | 16-lead TSSOP | 14-lead TSSOP | Different pin counts and footprints prevent drop-in board replacement without layout changes. |
| Pin Count | 16 | 14 | Pin count mismatch means the parts are not pin-compatible and cannot be swapped directly. |
| Operating Temperature Range | -40°C to +85°C | -40°C to +85°C | Both share the same industrial temperature range, so thermal environment is not a differentiator. |
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Full specification comparison
Use manufacturer datasheets as the final authority.
| Specification | AD8304ARU | AD8309ARUZ |
|---|---|---|
| Part Status | Obsolete | Active |
| Base Product Number | AD8304 | - |
| Type | Logarithmic Converter | Logarithmic Amplifier |
| Applications | Fiber Optics | Receiver Signal Strength Indication (RSSI) |
| Mounting Type | Surface Mount | Surface Mount |
| Packaging | Tube | - |
Frequently asked questions
What are the primary functional differences between the AD8309ARUZ and the AD8304ARU?
The AD8309ARUZ is a 100 dB demodulating logarithmic amplifier with a limiting output, intended for RSSI and signal-strength measurement applications. The AD8304ARU is a 160 dB logarithmic converter optimized for photodiode current measurement in fiber-optic and optical power monitoring applications. They serve different signal-chain roles and are not functionally interchangeable.
Do the AD8309ARUZ and AD8304ARU use the same package and pinout?
Both devices are offered in a 14-lead TSSOP package (RU suffix), but their pin functions and internal signal paths differ. The AD8309 provides logarithmic limiting output and RSSI functionality, while the AD8304 provides a logarithmic voltage output proportional to input current. PCB layout and pin connections must follow each device's respective datasheet and cannot be treated as pin-compatible.
What is the specified dynamic range of each device?
The AD8309ARUZ provides approximately 100 dB of demodulating logarithmic dynamic range. The AD8304ARU provides a 160 dB logarithmic conversion range for input currents, typically spanning from picoamps to milliamps as specified in its datasheet. The wider range of the AD8304 reflects its photodiode-current measurement application.
Can the AD8304ARU be used as a direct replacement for the AD8309ARUZ in an RSSI circuit?
No. The AD8309ARUZ is designed for RF signal-strength indication with a limiting output, while the AD8304ARU is a logarithmic current-to-voltage converter for photodiode monitoring. Their input interfaces, output formats, and frequency behavior differ, so direct substitution is not supported without redesign and validation against the manufacturer datasheets.
What are the typical operating frequency or bandwidth specifications for these parts?
The AD8309ARUZ is specified for operation over a wide RF input range with a limiting output bandwidth suitable for signal-strength measurement in receiver chains. The AD8304ARU is specified for logarithmic current conversion with bandwidth characteristics defined for optical power monitoring. Designers should consult the respective datasheets for exact frequency and response specifications before selecting a part.
Are both devices available in RoHS-compliant packaging?
The AD8309ARUZ and AD8304ARU are both offered in TSSOP packages, and the "Z" suffix on the AD8309ARUZ indicates RoHS-compliant packaging per Analog Devices' part-numbering convention. Designers should verify the specific ordering code and compliance status on the manufacturer or authorized distributor listing for the exact variant required.
Which device is better suited for optical power monitoring?
The AD8304ARU is the appropriate choice for optical power monitoring because it is a 160 dB logarithmic converter designed to interface with photodiodes and produce a logarithmic voltage output proportional to input current. The AD8309ARUZ is intended for RF demodulating logarithmic amplification and RSSI applications rather than photodiode current measurement.