![]() The following series of illustrations shows this for three input states (00, 01, and 10): Namely, if either of the inputs is grounded, transistor Q2 will be forced into a condition of cutoff, thus turning Q3 off and floating the output (output goes “high”). ![]() Since this circuit bears so much resemblance to the simple inverter circuit, the only difference being a second input terminal connected in the same way to the base of transistor Q2, we can say that each of the inputs will have the same effect on the output. Thus, a 1 in resulted in a 0 out, and vice versa. In the case of the open-collector output configuration, this “high” state was simply “floating.”Īllowing the input to float (or be connected to Vcc) resulted in the output becoming grounded, which is the “low” or 0 state. In the single-input (inverter) circuit, grounding the input resulted in an output that assumed the “high” (1) state. This transistor has one collector, one base, and two emitters, and in the circuit, it looks like this: Unfortunately, a simple NPN transistor structure is inadequate to simulate the three PN junctions necessary in this diode network, so a different transistor (and symbol) is needed. Just as in the case of the inverter and buffer, the “steering” diode cluster marked “Q1” is actually formed like a transistor, even though it isn’t used in any amplifying capacity. This schematic illustrates a real circuit, but it isn’t called a “two-input inverter.” Through analysis, we will discover what this Circuit’s logic function is and correspondingly what it should be designated as. Data Bits The bit width of the component's inputs and outputs.Suppose we altered our basic open-collector inverter circuit, adding a second input terminal just like the first: Gate Location The location of the gate input. Facing The direction of the component (its output relative to its input). Type Determines whether the transistor is P-type or N-type. When the component is selected or being added,Īlt-0 through Alt-9 alter its Data Bits attributeĪnd the arrow keys alter its Facing attribute. Or an error value, then the output will be an error value. Input is the negation of what indicates negation. If indicated by the gate input, or will be floating if the gate East edge (output, bit width matches Data Bits attribute) The component's output, which will match the source input This will trigger the transistor if the gate value is 1. Will transmit if the gate value is 0 for N-type transistors, North edge (input, bit width 1) The component's gate input. Pins (assuming component faces east, gate line top/left) West edge (input, bit width matches Data Bits attribute) The component's source input that will transmit to the output Is that a transistor is meant for more basic circuit designs. If the Data Bits attribute is more than 1, the gate input is stillĪ single bit, but its value is applied simultaneously to each of theĪn N-type transistor behaves very similarly to aĬontrolled Buffer. * If source is Z, drain is Z otherwise drain is X. When gate is 0, while an N-type transistor (which has no such circle) (indicated by a circle on the gate line) transmits The determination of transmitting or disconnectingĭepends on the type of transistor: A P-type transistor The value at source may be transmitted toĭrain or there may be no connection from source, Plate, while the N-type transistor has no such circle. Transistor is indicated by a circle connecting the gate input to its Transistors, with slightly different behaviors described below the P-type ![]() The gate input is drawn connected to a plate that is parallel to the Logisim draws an arrowhead to indicate the direction of flow from input to output. Input and drain output are drawn connected by a plate A transistor has two inputs, called gate and source,Īnd one output, called drain. ![]()
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