Methods of and apparatus for trimming film resistors

A method of trimming a film resistor which comprises the steps of:

• connecting the resistor in a gain-producing circuit;
• establishing a first gain level related to a value of resistance of the resistor below a first-trimmed value of the resistor to which the resistor is to be trimmed;
• trimming the resistor to increase the gain to the established first gain level wherein the resistance value is now the first-trimmed value;
• establishing a second gain level for the gain-producing circuit related to a basic resistance value of the resistor;
• selectively adding resistance to the resistor in the gain-producing circuit to increase the gain to a level not to exceed the second gain level;
• adding the first-trimmed value of the resistor and the value of the selectively added resistance to obtain the basic resistance value;
• trimming further the resistor to increase the value thereof to a second-trimmed value;
• and
• stopping the trimming of the resistor when the second-trimmed value thereof is equal to the basic resistance value.

A method of trimming a film resistor, which comprises the steps of:

• connecting the resistor in a gain-producing circuit;
• determining the resistance value of the resistor;
• establishing a gain level for the gain-producing circuit related to a basic resistance value of the resistor;
• selectively adding resistance to the resistor in the gain-producing circuit to increase the gain to a level not to exceed the established gain level;
• adding the determined value of the resistor and the value of the selectively added resistance to obtain the basic resistance value;
• selecting a trim target resistance value less than the basic resistance value;
• trimming the resistor to increase the value thereof;
• and
• stopping the trimming of the resistor when the trimmed value is equal to the trim target resistance value.

An apparatus for trimming a film resistor, which comprises:

• a gain-producing circuit;
• means for determining the resistance value of the resistor;
• means for connecting the resistor in the gain-producing circuit;
• means for establishing a gain level for the gain-producing circuit related to a basic resistance value of the resistor;
• means for selectively adding resistance to the resistor in the gain-producing circuit to increase the gain to a level not to exceed the gain level determined by the establishing means;
• means for adding the determined value of the resistor and the value of resistance determined by the selectively adding means to produce the basic resistance value;
• means for trimming the resistor to increase the value thereof;
• and
• means for stopping the trimming of the resistor when the trimmed value thereof is equal to the basic value.

An apparatus for trimming a film resistor, which comprises:

• a gain-producing circuit;
• means for connecting the resistor in the gain-producing circuit
• means for establishing a first gain level related to a value of resistance of the resistor below a first-trimmed value of the resistor to which the resistor is to be trimmed;
• means for trimming the resistor to increase the gain to a level determined by the first gain establishing means where the resistance value is now the first-trimmed value;
• means for establishing a second gain level for the gain-producing circuit related to a basic resistance value of the resistor;
• means for selectively adding resistance to the resistor in the gain-producing circuit to increase the gain to a level not to exceed the gain level determined by the second gain level establishing means;
• means for adding the first-trimmed value of the resistor and the value of resistance determined by the selectively adding means to produce the basic resistance value;
• means for trimming the resistor to increase the value thereof to a second-trimmed value;
• and
• means for stopping the trimming of the resistor when the second-trimmed value thereof is equal to the basic resistance value.

An apparatus for trimming a resistor, which comprises:

• a gain producing circuit;
• means for connecting the resistor in the gain-producing circuit;
• means for determining the resistance value of the resistor;
• means for establishing a gain level for the gain-producing circuit related to a basic resistance value of the resistor;
• means for selectively adding resistance to the resistor in the gain-producing circuit to increase the gain to a level not to exceed the gain level determined by the establishing means;
• means for adding the determined value of the resistor and the value of resistance determined by the selectively adding means to produce the basic resistance value;
• means for selecting a trim target resistance value less than the basic resistance value;
• means for trimming the resistor to increase the value thereof;
• and
• means for stopping the trimming of the resistor when the trimmed value is equal to the trim target resistance value.

A method of trimming a film resistor which comprises the steps of:

• connecting the resistor in a gain-producing circuit;
• establishing a gain level related to a value of resistance to which the resistor is to be trimmed on a first-trimmed value of the resistor;
• trimming the resistor to increase the gain to the established gain level wherein the resistance value is now the first-trimmed value;
• establishing a basic resistance value which is greater than the first-trimmed value of the resistor to be trimmed;
• trimming the resistor to increase the value thereof;
• and
• stopping the trimming of the resistor when the trimmed value thereof is equal to the basic resistance value.