Bardeen and Brattain Point-Contact Transistor
US 2,524,035Forward emitter injection and reverse collector capture in a semiconductor surface layer
How It Works: Step-by-Step Mechanical & Physical Breakdown
Forward emitter bias injects carriers into the surface layer; a nearby reverse-biased collector shapes an electric field and captures part of the spreading carrier current. A small emitter signal changes collector current through a high load impedance, enabling voltage and power gain.
Interactive Real-Time Physical Simulation
Detailed Component Architecture
1Supporting semiconductor body
The source distinguishes N- and P-type carrier populations and places the base at low resistance to the body; surface and bulk are separated by a high-resistance barrier where specified.
2Emitter and collector contacts
The emitter is forward-biased and the collector reverse-biased. Their short separation lets current spread in the layer and enter the collector field before it crosses to the base.
3Bias and external circuits
The patent identifies conventional, grounded-grid, grounded-plate, and feedback connections, but makes the carrier and polarity conditions—not a tube metaphor—the operating limitation.
Governing Equations & Engineering Principles
Point-Contact Minority Hole Injection & Dynamic Current Amplification
Solid-State Semiconductor PhysicsClaim 1Current Gain Factor
In point-contact transistors, holes injected from the gold foil emitter create an electron-trapping space charge that pulls multiple electrons from the base into the collector, yielding alpha > 1.
Bardeen and Brattain discovered that pressing two gold-leaf contacts onto a germanium crystal just 0.002 inches apart allowed holes injected by the emitter to control the reverse current of the collector, creating the world's first solid-state amplifier.
Historical Context: US 2,524,035 describes a three-electrode semiconductor circuit element using close emitter and collector contacts to translate an input variation into a collector-current variation.
Einstein Relation for Semiconductor Carrier Diffusion
Solid-State Physics & ThermodynamicsClaim 2Minority Hole Diffusivity
Determines how quickly minority holes transit the space-charge inversion layer between emitter and collector.
The Einstein relation bridges thermodynamics and electromagnetism, proving that charge carriers diffuse at a rate dictated solely by their mobility and thermal kinetic energy.
Historical Context: Enabled accurate analytical modeling of bipolar junction and point-contact transistor frequency response.
Interactive Schematic Sheet (Fig. 1)
The printed drawing shows block 1, plated base 2, surface layer 3, barrier 4, emitter 5, collector 6, and the input/output transformers.
Select Any Numbered Pin
Click pins on the schematic or select from the list below to inspect historical specifications.
Why It Still Matters
The grant documents an early practical solid-state amplifier and articulates the carrier, contact, impedance, and bias relationships that made transistor action an engineered circuit element rather than a rectifier alone.
Legal Claims Decoder (40 Numbered Claims)
The Historical Bottleneck
Why Prior Art Failed
- •Earlier solid rectifier amplifier proposals relied on embedded grids or transverse fields that the specification says were too fine to fabricate successfully.