BJT operating biases (NPN): For normal forward-active operation, the base must be ________ with respect to the emitter, and ________ with respect to the collector.

Introduction / Context:
Bias conditions determine a BJT’s operating region. For an NPN transistor used as an amplifier in forward-active mode, the base-emitter junction is forward biased and the collector-base junction is reverse biased.

Given Data / Assumptions:

• Device: NPN BJT.
• Desired region: forward-active (normal operation for amplification).
• Polarity conventions referenced to the base node.

Concept / Approach:
Forward bias of the base-emitter junction requires V_BE > 0 (typically about +0.6 to +0.7 V for silicon). Reverse bias of the collector-base junction requires the collector to be at a higher potential than the base in an NPN, making the base negative relative to the collector.

Step-by-Step Solution:
Forward-active requires: base more positive than emitter → base-emitter junction forward biased.Simultaneously, collector more positive than base → base is negative with respect to the collector (C > B).Therefore, the base is positive with respect to the emitter and negative with respect to the collector.

Verification / Alternative check:
Typical bias example: E = 0 V, B ≈ +0.7 V, C ≈ +5 V. Here B is +0.7 V above E (forward bias), and B is 4.3 V below C (reverse bias of C-B junction), confirming forward-active conditions.

Why Other Options Are Wrong:
Positive, positive: Makes C-B not reverse biased if C is not sufficiently above B.Negative, positive / negative, negative / zero, zero: Would not forward-bias B-E properly and would not reverse-bias C-B as required.

Common Pitfalls:
Mixing up PNP vs. NPN polarities, or assuming saturation (both junctions forward-biased) is “normal” operation for linear amplification.

Final Answer:
positive, negative