Why Your HV Measurement Circuit Is Lying to You

Here is a number that keeps precision engineers awake at night: 1 nA. One nanoampere of reverse leakage in a high-voltage diode. In a power supply, that is negligible. In a sensitive measurement circuit — a photomultiplier bias chain, a mass spectrometer detector, an electrophoresis high-voltage stack — it is catastrophic. The signals you are trying to measure exist at the picoampere level. A leaking diode does not just add noise; it completely swamps the signal, rendering your instrument useless.

The physics are unforgiving. Under high reverse bias, three mechanisms conspire against you: thermal generation of electron-hole pairs in the depletion region, quantum tunneling through the potential barrier, and surface leakage along the semiconductor-passivation interface. The cruel irony? To achieve higher blocking voltage, you need thicker, lighter-doped material — which increases the volume where thermal generation occurs. Higher voltage and lower leakage are fundamentally at war with each other, and your diode sits at the crossfire.

If your current diode supplier treats low leakage as an afterthought — or worse, has stopped manufacturing the low-leakage parts you specified years ago — your measurement integrity hangs by a thread.

HVD Series: Low-Leakage HV Diodes That Let Your Signal Through

HVC's HVD series high-voltage rectifier diodes are engineered from the silicon die up for exactly this scenario: precision measurement applications where reverse leakage must stay in the picoampere range, not nanoamperes.

How We Keep Leakage in the Picoampere Range

• Crystal-grade silicon substrates: Minimal defects and impurities that act as generation-recombination centers — the primary source of thermal leakage current
• Optimized edge termination: Field plates and guard rings that smooth electric field distribution at the junction periphery, eliminating field crowding that causes premature breakdown and localized leakage hotspots
• Advanced surface passivation: Thermally grown oxide and deposited nitride layers that tie up dangling bonds and eliminate surface conduction paths — the silent killer in many "low-leakage" diodes
• Hermetic packaging: Ceramic and glass-header sealed packages that block ambient humidity and contaminants from creating parasitic conduction paths over the component's lifetime

Direct Replacements for the Brands You Already Specify

The Missing Half of the Equation: Why Diodes Alone Are Not Enough

A low-leakage diode is necessary but not sufficient. In a voltage multiplier, DC-DC converter, or Cockcroft-Walton stack, the diode controls charge transfer efficiency — but it is the capacitors that determine output ripple, voltage stability, and noise floor. Pair a world-class low-leakage diode with a mediocre capacitor that has high dielectric absorption or insulation resistance drift, and you have wasted your money on the diode.

This is why HVC also manufactures the capacitors that complete the precision HV power chain:

HVCT8G Doorknob Capacitors — Ultra-Stable Filtering, 10kV–150kV

When your detector bias supply must hold rock-steady within millivolts across temperature swings, the N4700 Class I dielectric in our HVCT8G series delivers: dissipation factor below 0.1%, insulation resistance exceeding 200,000 megohms, and capacitance stability within +/-5% from -30C to +85C. These are the direct replacements for the discontinued Murata DHS series that many precision instruments were designed around — same mounting footprint, same thread options (M4/M5/M6 and UNF 10-32), zero board rework required.

HVR/GHP Precision Resistors — The Voltage Divider That Does Not Drift

In a precision HV divider chain, resistor voltage coefficient (VCR) is the silent enemy. A 100 megohm divider that shifts 2% under full voltage produces a 2% measurement error — and you will never see it on a low-voltage bench test. HVC HVR series thick film resistors maintain VCR below 5 ppm/V and resistance stability within 0.5% over 1,000-hour full-load testing. Direct replacements for Vishay FHV, Caddock TG/MG, and Ohmite MOX series — with 4–8 week lead times instead of 20–40 weeks.

System-Level Design: Stopping Leakage at Every Level

Selecting low-leakage components is only the beginning. Your PCB, connectors, and layout must match the same exacting standard:

• PTFE substrates: High surface resistivity and low hygroscopicity — FR-4 is not acceptable for picoampere circuits
• Guard rings on every high-impedance node: Actively driven traces that eliminate potential gradients driving stray currents
• Shielded pre-amplifier enclosures: Physical guarding against electrostatic interference at the most vulnerable stage
• Linear regulation, not switching: Any ripple on the HV rail couples directly into the signal path in high-impedance circuits
• Route discipline: HV traces must never run parallel to high-impedance input lines — capacitive coupling is a leakage pathway too

One Supplier. Complete HV Power Chain. No Finger-Pointing.

When your measurement instrument fails, you do not want to hear "it is the diode" from the capacitor vendor and "it is the capacitor" from the diode vendor. HVC manufactures all three critical components in the precision HV power chain — diodes, capacitors, and resistors — under one roof. That means:

• Guaranteed compatibility: We specify and test our diodes, capacitors, and resistors to work together — no unpleasant integration surprises
• Single-source accountability: One engineering team understands your entire HV chain and can diagnose cross-component issues
• Consistent supply chain: Vertically integrated from ceramic powder to finished product — no 30-week lead times, no EOL surprises
• Drop-in replacements: Pin-to-pin compatible with HVCA/CKE, EDI, VMI, Murata, Vishay, Caddock — no board redesign needed

Stop Fighting Leakage. Start Measuring Signal.

Your sensitive measurement circuit deserves better than diodes that leak, capacitors that drift, and resistors that shift under voltage. HVC's HVD diodes, HVCT8G capacitors, and HVR resistors are engineered to keep your signal path clean from the HV power supply to the detector input — and they drop right into the footprints your board was designed for.

Whether you are building the next generation of mass spectrometers, upgrading aging X-ray HV multipliers, or replacing obsolete Sanken and HVCA diode parts in fielded instruments, we have the low-leakage components and the application engineering support to make it work.