Agilent Technologies B1500A Manual de servicio Pagina 52

  • Descarga
  • Añadir a mis manuales
  • Imprimir
  • Pagina
    / 110
  • Tabla de contenidos
  • MARCADORES
  • Valorado. / 5. Basado en revisión del cliente
Vista de pagina 51
Module 5
Basic Measurement
5-32
Simplified Diagram
x1
Buffer
SMU
DUT
Force
V
Guard
Rs
10K
Guard Connection for Non-Kelvin Connection
The guard connection is needed for measurement < 1 nA. Below 1 nA a regular coax cable's
capacitance dominates over the DUT (device under test) capacitance. What you see is cable
charging current. I = C(dv/dt) where dv/dt is the rate of change of SMU voltage from one step to the
next of a coax cable with no guard. C is the total capacitance of the cable.
The above diagram shows how the cable capacitance is eliminated with a triaxial cable. The guard is
driven at the same voltage as the force center conductor. No current can flow between guard and
force when they are held at the same potential. Guard and force are isolated by a buffer amplifier.
They can never be shorted together.
Vista de pagina 51
1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 109 110

Comentarios a estos manuales

Sin comentarios