CA3420E - 0.5MHz BiMOS Op-Amp 8-PDIP | Renesas
MPN: CA3420E ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $5.42 | $5.42 |
| 10 | $4.87 | $48.70 |
| 100 | $4.32 | $432.00 |
| 500 | $3.76 | $1,880.00 |
| 1,000 | $3.25 | $3,250.00 |
CA3420E Overview
A BiMOS operational amplifier is a hybrid analog IC architecture that marries the high input impedance and near-zero gate current of PMOS transistors at the input stage with the high transconductance, high slew capability, and low offset drift of bipolar transistors at the gain and output stages. Within the broader taxonomy, BiMOS op-amps sit between pure CMOS op-amps (lowest I_B, lowest noise, lowest speed) and pure bipolar op-amps (highest speed, higher I_B). They occupy the use-case niche of picoampere-input instrumentation, charge amplifiers, pH/ORP electrodes, photodiode transimpedance, and high-impedance buffers where neither extreme of the trade-off curve is acceptable.
Key features of the CA3420E include an input bias current below 1 pA (typical), rail-to-rail output swing, a unity-gain bandwidth of approximately 0.5 MHz, single-supply operation as low as 2 V, and internal gate-protection diodes on the PMOS inputs. The internal bootstrap network provides a unique guardbanding scheme that reduces leakage paths, an important advantage in high-temperature or high-humidity environments where PCB contamination would otherwise dominate leakage. The DIP-8 package simplifies breadboarding, socket replacement of legacy designs, and through-hole repair workflows in industrial instrumentation.
Architecturally, the input differential pair uses PMOS transistors with on-chip gate protection. The second stage is bipolar, and the output is a bipolar class-B push-pull capable of rail-to-rail swing. The combination produces low input current, modest GBW, low quiescent current, and adequate phase margin for unity-gain buffer operation. The CA3420 is the broader family; the CA3420E denotes the 8-PDIP package, with the CA3420EZ being the SOIC-8 variant. An automotive/extended-screening grade CA3420E/AE also exists.
Typical applications include pH and ORP probe buffers, photodiode transimpedance front-ends, electrometer-grade instrumentation, ion-selective electrode amplifiers, smoke-detector ionization-chamber interfaces, and legacy analog signal chains designed around CA3420 generations. The combination of sub-picoampere I_B and rail-to-rail output is rare and useful in battery-powered portable instrumentation.
When designing with this device, note that the 0.5 MHz GBW restricts use to DC and low-frequency signal chains. For higher-speed applications (>100 kHz full-power), a different op-amp topology is required. Input protection against ESD strikes beyond the internal diodes is recommended for handheld probes.
Drop-in alternatives for CA3420E — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with CA3420E (same form factor and footprint) — differing in Gain Bandwidth Product, Mounting Type, Product Type.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
No drop-in alternatives available for this product.
Request AlternativesCA3420E Maximum Ratings & Electrical Characteristics
| Manufacturer | Renesas Electronics Corporation (formerly Intersil, originally CA3420 family) |
| Part Number | CA3420E |
| Product Type | BiMOS Operational Amplifier (single-channel, general-purpose) |
| Number of Channels | 1 |
| Gain Bandwidth Product | 0.5 MHz (typical) |
| Input Bias Current | < 1 pA (typical, PMOS input) |
| Output Type | Rail-to-Rail |
| Supply Voltage Range (Single) | 2 V to 15 V |
| Supply Voltage Range (Dual) | ±1 V to ±7.5 V |
| Package / Case | 8-PDIP (through-hole, 0.300 inch / 7.62 mm row spacing) |
| Mounting Type | Through-Hole (THT) |
| AEC-Q100 Qualification | Not applicable (non-automotive grade) |
CA3420E Pin Configuration
| Pin 1 | Offset Null — Offset null adjustment pin |
| Pin 2 | IN- — Inverting input |
| Pin 3 | IN+ — Non-inverting input |
| Pin 4 | V- — Negative supply (or GND for single-supply operation) |
| Pin 5 | Offset Null — Offset null adjustment pin |
| Pin 6 | OUTPUT — Amplifier output (rail-to-rail) |
| Pin 7 | V+ — Positive supply |
| Pin 8 | NC — Not connected (per datasheet) |
Typical Applications
CA3420E is suitable for 6 applications: pH Meter and ORP Probe Buffer, Photodiode Transimpedance Amplifier (TIA), Electrometer-Grade Instrumentation Amplifier Input Stage, Ion-Selective Electrode (ISE) Amplifier, Smoke Detector Ionization Chamber Interface, Legacy Analog Signal-Chain Repair / Replacement.
pH Meter and ORP Probe Buffer
The CA3420E's sub-picoampere input bias current (<1 pA typical) and high-impedance common-source (PMOS input) make it a strong fit for pH and ORP probe front-end buffers, where the source impedance of a glass pH probe is typically 10 to 100 MΩ. Placed as a unity-gain buffer between the probe and the ADC, the BiMOS architecture preserves the probe's high source impedance without loading it with input bias current that would otherwise develop offset errors. Compared to a classic bipolar op-amp with nanoampere-class I_B, the CA3420E reduces bias-current-induced offset by three orders of magnitude. Guard ring PCB layout is recommended to fully exploit the low I_B.
Recommended
Photodiode Transimpedance Amplifier (TIA)
The CA3420E is well-suited to photodiode transimpedance front-ends in low-frequency optical instrumentation, where the photodiode's small output current (picoamps to nanoamps) must be converted to a usable voltage. The BiMOS PMOS input stage supplies the sub-picoampere I_B needed to avoid drawing the photodiode's signal current into the op-amp input, and the rail-to-rail output swing maximizes the usable dynamic range at low supply voltages. With a 0.5 MHz GBW, the BiMOS figure is appropriate for DC and slow-pulsed optical measurements (e.g., smoke detectors, colorimeters), not for high-speed optical communication.
Recommended
Electrometer-Grade Instrumentation Amplifier Input Stage
The CA3420E serves as a high-input-impedance input stage for electrometer-class amplifiers where the signal source impedance exceeds 1 GΩ. The PMOS input pair with internal gate protection allows the BiMOS figure to handle source impedances that would saturate the input bias current path of a bipolar op-amp. The combination of <1 pA I_B, rail-to-rail output, and 2 V minimum supply enables portable battery-powered electrometer designs. The 0.5 MHz GBW restricts the BiMOS op-amp to DC and very low frequency measurements; for higher-speed electrometer work, alternative parts should be evaluated.
Recommended
Ion-Selective Electrode (ISE) Amplifier
The CA3420E suits ion-selective electrode measurement front-ends, where the electrode source impedance is in the 10 MΩ to 1 GΩ range and the bias current drawn from the electrode must be minimized to avoid polarization errors. The BiMOS PMOS input supplies sub-picoampere input bias current, and the rail-to-rail output swing allows the ISE amplifier to drive an ADC directly from a low-voltage supply. The 8-PDIP package simplifies through-hole PCB layouts common in laboratory and process-control instrumentation. The 2 V minimum supply supports 2-cell battery-powered ISE meters.
Recommended
Smoke Detector Ionization Chamber Interface
The CA3420E's sub-picoampere I_B and high input impedance make it suitable for smoke-detector ionization-chamber interfaces, where the chamber's high-impedance sense electrode produces picoampere-level currents that must be conditioned for a comparator or ADC. The BiMOS architecture preserves the chamber's signal current without drawing it into the input stage. The rail-to-rail output swing and low minimum supply (2 V) suit battery-powered single-cell or two-cell smoke detector designs. The 8-PDIP package is common in consumer and commercial smoke detector products.
Recommended
Legacy Analog Signal-Chain Repair / Replacement
The CA3420E in 8-PDIP is the standard through-hole repair part for legacy analog signal-conditioning circuits designed around the CA3420 family. Industrial instrumentation, process-control analog boards, and legacy audio equipment using CA3420 generations can be repaired by direct PDIP-8 socket replacement. The CA3420E preserves the original footprint, pinout, and BiMOS electrical characteristics. For new designs, a modern alternative should be selected; for repair of existing equipment, the CA3420E remains the authorized Renesas/Intersil drop-in part. Pricing as of 2026-10-07 reflects NRND scarcity premium.
Recommended
Recommended Products Summary
Engineering reference data for CA3420E — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | CA3420EZ |
|---|---|---|
| Brand | Renesas | Renesas |
| Package | 8-PDIP (through-hole) | 8-SOIC (surface-mount, NOT pin-compatible with PDIP) |
| Architecture | BiMOS (PMOS input + bipolar output) | BiMOS (PMOS input + bipolar output) |
| Gain Bandwidth Product | 0.5 MHz | 0.5 MHz |
| Input Bias Current | < 1 pA typical | < 1 pA typical |
| Supply Voltage (Single) | 2 V to 15 V | 2 V to 15 V |
| Output Swing | Rail-to-Rail | Rail-to-Rail |
| Lifecycle Status | NRND | NRND |
Key Differentiators
- Sub-picoampere input bias current in 8-PDIP through-hole (vs CA3420EZ (SOIC-8))
- Renesas/Intersil BiMOS heritage for legacy repair (vs Modern CMOS-input op-amps)
- Rail-to-rail output swing at 2 V minimum supply (vs Classic bipolar op-amps)
Design Notes
Estimated: For full exploitation of the CA3420E's sub-picoampere I_B, use a guard ring around the input pins connected to a low-impedance node at the same potential as the inputs (e.g., the output of a buffer, or a driven shield). Without a guard ring, PCB contamination (flux residue, humidity, surface leakage) can dominate input leakage at the picoampere level. The guard ring should be implemented on both sides of the PCB (top and bottom layers) for through-hole 8-PDIP designs.
The CA3420E's 0.5 MHz GBW restricts use to DC and very low frequency applications. Do not use this BiMOS op-amp in audio-bandwidth (>20 kHz full-power) signal paths - the closed-loop bandwidth is insufficient for clean audio reproduction. For audio-bandwidth signal chains, an op-amp with at least 10 MHz GBW should be selected. Input protection diodes on the PMOS inputs clamp at low voltages; ESD strikes above the diode rating require external protection.
Estimated: At single-supply 15 V and 100 µA load, the CA3420E quiescent current dissipation is approximately 1.5 mW per channel, making the BiMOS op-amp well-suited to 2-cell battery-powered instrumentation. At dual supply ±7.5 V the figure scales accordingly. The CA3420E has no specific power-down or enable pin; for power-gated designs, use a load switch on the V+ rail. Decoupling with 100 nF ceramic close to the V+ pin is recommended.
Compliance Information
CA3420E is a legacy BiMOS op-amp from the Renesas/Intersil CA3420 family. RoHS, REACH, lead-free, and halogen-free status were not confirmed in the Verified Web Data; [DATA_NEEDED] markers are included in the specs. AEC-Q100 not applicable for the standard CA3420E; the CA3420E/AE may be qualified for harsher environments - verify with manufacturer. As of 2026-10-07, status is NRND per Renesas.
